[v2] tree-optimization: Canonicalize conditional signed narrow clips [PR127166]

Message ID 20260902054134.40540-1-ktkachov@nvidia.com
State Committed
Commit da3b0463f66312c9e93a027bae73bf17c24a8833
Headers
Series [v2] tree-optimization: Canonicalize conditional signed narrow clips [PR127166] |

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Commit Message

Kyrylo Tkachov Sept. 2, 2026, 5:41 a.m. UTC
  From: Kyrylo Tkachov <ktkachov@nvidia.com>

The PR120378 RISC-V tests use this source form:

  (NT) ((UT) x > NT_MAX ? (-x) >> (PREC - 1) : x)

For every defined execution, it is an unsigned saturating truncation of
MAX (x, 0).  The signed negation is undefined at the signed minimum under
the default overflow rules.

Loop if-conversion changes the selected negation to unsigned arithmetic.
This loses the distinction between the signed source and the explicit
unsigned-negation form from PR126981, which must not become a saturating
truncation.

Canonicalize the signed form while its overflow semantics are still
available before loop if-conversion:

  (NT) MIN ((UT) MAX (x, 0), NT_MAX)

Require an unsigned comparison, a signed right shift, undefined and
unsanitized negation overflow, exact constants, and no side effects.  This
keeps the original form with -fwrapv, -ftrapv, sanitization, volatile
operands, and explicit unsigned negation.

With this patch the tests restore the RISC-V saturation patterns.
Update pr103771.c because the direct form is
canonicalized before phiopt.

Bootstrapped and tested on aarch64-none-linux-gnu.
Ok for trunk?
Thanks,
Kyrill

gcc/ChangeLog:

	PR tree-optimization/127166
	* match.pd: Canonicalize conditional signed narrow clips before loop
	if-conversion.

gcc/testsuite/ChangeLog:

	PR tree-optimization/127166
	* gcc.dg/tree-ssa/pr103771.c: Check the earlier canonicalization.
	* gcc.dg/tree-ssa/pr127166.c: New test.
	* gcc.dg/tree-ssa/pr127166-3.c: New test.
	* gcc.dg/vect/pr127166.c: New test.
	* gcc.target/riscv/rvv/autovec/pr120378-1.c: Update expected dump
	counts.
	* gcc.target/riscv/rvv/autovec/pr120378-2.c: Request an optimized dump.
	* gcc.target/riscv/rvv/autovec/pr120378-3.c: Likewise.  Update expected
	dump counts.
	* gcc.target/riscv/rvv/autovec/pr120378-4.c: Request an optimized dump.

Signed-off-by: Kyrylo Tkachov <ktkachov@nvidia.com>
---
 gcc/match.pd                                  | 37 +++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr103771.c      |  5 +-
 gcc/testsuite/gcc.dg/tree-ssa/pr127166-3.c    | 15 ++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr127166.c      | 53 +++++++++++++++++++
 gcc/testsuite/gcc.dg/vect/pr127166.c          | 50 +++++++++++++++++
 .../gcc.target/riscv/rvv/autovec/pr120378-1.c |  4 +-
 .../gcc.target/riscv/rvv/autovec/pr120378-2.c |  2 +-
 .../gcc.target/riscv/rvv/autovec/pr120378-3.c |  6 +--
 .../gcc.target/riscv/rvv/autovec/pr120378-4.c |  2 +-
 9 files changed, 165 insertions(+), 9 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr127166-3.c
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr127166.c
 create mode 100644 gcc/testsuite/gcc.dg/vect/pr127166.c
  

Comments

Richard Biener Sept. 2, 2026, 7:36 a.m. UTC | #1
On Wed, 2 Sep 2026, ktkachov@nvidia.com wrote:

> From: Kyrylo Tkachov <ktkachov@nvidia.com>
> 
> The PR120378 RISC-V tests use this source form:
> 
>   (NT) ((UT) x > NT_MAX ? (-x) >> (PREC - 1) : x)
> 
> For every defined execution, it is an unsigned saturating truncation of
> MAX (x, 0).  The signed negation is undefined at the signed minimum under
> the default overflow rules.
> 
> Loop if-conversion changes the selected negation to unsigned arithmetic.
> This loses the distinction between the signed source and the explicit
> unsigned-negation form from PR126981, which must not become a saturating
> truncation.
> 
> Canonicalize the signed form while its overflow semantics are still
> available before loop if-conversion:
> 
>   (NT) MIN ((UT) MAX (x, 0), NT_MAX)
> 
> Require an unsigned comparison, a signed right shift, undefined and
> unsanitized negation overflow, exact constants, and no side effects.  This
> keeps the original form with -fwrapv, -ftrapv, sanitization, volatile
> operands, and explicit unsigned negation.
> 
> With this patch the tests restore the RISC-V saturation patterns.
> Update pr103771.c because the direct form is
> canonicalized before phiopt.
> 
> Bootstrapped and tested on aarch64-none-linux-gnu.
> Ok for trunk?

OK.

Thanks,
Richard.

> Thanks,
> Kyrill
> 
> gcc/ChangeLog:
> 
> 	PR tree-optimization/127166
> 	* match.pd: Canonicalize conditional signed narrow clips before loop
> 	if-conversion.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR tree-optimization/127166
> 	* gcc.dg/tree-ssa/pr103771.c: Check the earlier canonicalization.
> 	* gcc.dg/tree-ssa/pr127166.c: New test.
> 	* gcc.dg/tree-ssa/pr127166-3.c: New test.
> 	* gcc.dg/vect/pr127166.c: New test.
> 	* gcc.target/riscv/rvv/autovec/pr120378-1.c: Update expected dump
> 	counts.
> 	* gcc.target/riscv/rvv/autovec/pr120378-2.c: Request an optimized dump.
> 	* gcc.target/riscv/rvv/autovec/pr120378-3.c: Likewise.  Update expected
> 	dump counts.
> 	* gcc.target/riscv/rvv/autovec/pr120378-4.c: Request an optimized dump.
> 
> Signed-off-by: Kyrylo Tkachov <ktkachov@nvidia.com>
> ---
>  gcc/match.pd                                  | 37 +++++++++++++
>  gcc/testsuite/gcc.dg/tree-ssa/pr103771.c      |  5 +-
>  gcc/testsuite/gcc.dg/tree-ssa/pr127166-3.c    | 15 ++++++
>  gcc/testsuite/gcc.dg/tree-ssa/pr127166.c      | 53 +++++++++++++++++++
>  gcc/testsuite/gcc.dg/vect/pr127166.c          | 50 +++++++++++++++++
>  .../gcc.target/riscv/rvv/autovec/pr120378-1.c |  4 +-
>  .../gcc.target/riscv/rvv/autovec/pr120378-2.c |  2 +-
>  .../gcc.target/riscv/rvv/autovec/pr120378-3.c |  6 +--
>  .../gcc.target/riscv/rvv/autovec/pr120378-4.c |  2 +-
>  9 files changed, 165 insertions(+), 9 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr127166-3.c
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr127166.c
>  create mode 100644 gcc/testsuite/gcc.dg/vect/pr127166.c
> 
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 5777c833896..54cad1cd2bc 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -13372,6 +13372,43 @@ and,
>   (BUILT_IN_CONSTANT_P (nop_convert@1 @0))
>   (BUILT_IN_CONSTANT_P @0))
>  
> +/* Canonicalize a conditional signed narrow clip while the signed negation
> +   has its original overflow semantics:
> +
> +     (NT) ((UT) X > NT_MAX ? (-X) >> (PREC - 1) : X)
> +       -> (NT) MIN ((UT) MAX (X, 0), NT_MAX).  */
> +(if (INTEGRAL_TYPE_P (type) && TYPE_UNSIGNED (type))
> + (simplify
> +  (cond (gt (nop_convert@4 @0) INTEGER_CST@1)
> +	(convert (rshift@5
> +		  (nop_convert? (negate@3 (nop_convert? @0)))
> +		  INTEGER_CST@2))
> +	(convert @0))
> +  (if (!TREE_SIDE_EFFECTS (@0)
> +	&& !TYPE_UNSIGNED (TREE_TYPE (@0))
> +	&& TYPE_UNSIGNED (TREE_TYPE (@4))
> +	&& !TYPE_UNSIGNED (TREE_TYPE (@5))
> +	&& TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@3))
> +	&& !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@3)))
> +   (with
> +    {
> +     tree utype = TREE_TYPE (@4);
> +     unsigned itype_precision = TYPE_PRECISION (TREE_TYPE (@0));
> +     unsigned otype_precision = TYPE_PRECISION (type);
> +     wide_int trunc_max = wi::mask (otype_precision, false, itype_precision);
> +     wide_int int_cst_1 = wi::to_wide (@1, itype_precision);
> +     wide_int int_cst_2 = wi::to_wide (@2, itype_precision);
> +     wide_int shift_amount = wi::uhwi (itype_precision - 1,
> +				  itype_precision);
> +    }
> +    (if (otype_precision < itype_precision
> +	 && wi::eq_p (trunc_max, int_cst_1)
> +	 && wi::eq_p (int_cst_2, shift_amount))
> +     (convert (min:utype
> +		(convert:utype
> +		 (max @0 { build_zero_cst (TREE_TYPE (@0)); }))
> +		@1)))))))
> +
>  #if GIMPLE
>  
>  /* Include the saturation alu match patterns.  */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr103771.c b/gcc/testsuite/gcc.dg/tree-ssa/pr103771.c
> index 8061e2df79e..b3dde923281 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/pr103771.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr103771.c
> @@ -1,6 +1,7 @@
>  /* { dg-do compile } */
> -/* { dg-options "-O3 -fdump-tree-phiopt1-details" } */
> -/* { dg-final { scan-tree-dump-times "changed to factor operation out from COND_EXPR." 1 "phiopt1" } } */
> +/* { dg-options "-O3 -fdump-tree-gimple" } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "gimple" } } */
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "gimple" } } */
>  
>  typedef unsigned char uint8_t;
>  
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr127166-3.c b/gcc/testsuite/gcc.dg/tree-ssa/pr127166-3.c
> new file mode 100644
> index 00000000000..266b0aac75a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr127166-3.c
> @@ -0,0 +1,15 @@
> +/* PR tree-optimization/127166 */
> +/* { dg-do compile } */
> +/* { dg-require-effective-target int32 } */
> +/* { dg-options "-O2 -fsanitize=signed-integer-overflow" } */
> +/* { dg-additional-options "-fdump-tree-optimized" } */
> +
> +unsigned short
> +f (int x)
> +{
> +  return ((unsigned int) x > 65535u ? (-x) >> 31 : x);
> +}
> +
> +/* Keep the conditional signed negation so that it is checked at runtime.  */
> +/* { dg-final { scan-tree-dump-not "MAX_EXPR|MIN_EXPR" "optimized" } } */
> +/* { dg-final { scan-tree-dump {\.UBSAN_CHECK_SUB} "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr127166.c b/gcc/testsuite/gcc.dg/tree-ssa/pr127166.c
> new file mode 100644
> index 00000000000..9bf89246dba
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr127166.c
> @@ -0,0 +1,53 @@
> +/* PR tree-optimization/127166 */
> +/* { dg-do compile } */
> +/* { dg-require-effective-target int32 } */
> +/* { dg-options "-O2 -fdump-tree-gimple -fdump-tree-phiopt2" } */
> +
> +unsigned short
> +signed_clip (int x)
> +{
> +  return ((unsigned int) x > 65535u ? (-x) >> 31 : x);
> +}
> +
> +unsigned short
> +unsigned_clip (int x)
> +{
> +  return ((unsigned int) x > 65535u
> +	  ? (int) (-(unsigned int) x) >> 31 : x);
> +}
> +
> +unsigned short
> +signed_split_clip (int x)
> +{
> +  int neg = -x;
> +  int sign = neg >> 31;
> +  unsigned short high = sign;
> +
> +  return ((unsigned int) x > 65535u ? high : x);
> +}
> +
> +unsigned short
> +unsigned_split_clip (int x)
> +{
> +  unsigned int ux = x;
> +  unsigned int neg = -ux;
> +  int sign = (int) neg >> 31;
> +  unsigned short high = sign;
> +
> +  return (ux > 65535u ? high : x);
> +}
> +
> +volatile int v;
> +
> +unsigned short
> +volatile_clip (void)
> +{
> +  return ((unsigned int) v > 65535u ? (-v) >> 31 : v);
> +}
> +
> +/* The direct signed form is canonicalized in GENERIC.  The split signed form
> +   is canonicalized in GIMPLE before loop if-conversion.  */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "gimple" } } */
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "gimple" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 2 "phiopt2" } } */
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR" 2 "phiopt2" } } */
> diff --git a/gcc/testsuite/gcc.dg/vect/pr127166.c b/gcc/testsuite/gcc.dg/vect/pr127166.c
> new file mode 100644
> index 00000000000..5bc59ad3769
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/pr127166.c
> @@ -0,0 +1,50 @@
> +/* PR tree-optimization/127166 */
> +/* { dg-additional-options "-fwrapv" } */
> +/* { dg-require-effective-target int32 } */
> +/* { dg-require-effective-target vect_int } */
> +
> +#include "tree-vect.h"
> +
> +#define N 64
> +
> +__attribute__ ((noipa)) void
> +clip (unsigned short *__restrict out, const int *__restrict in, int n)
> +{
> +  for (int i = 0; i < n; ++i)
> +    {
> +      int x = in[i];
> +      out[i] = ((unsigned int) x > 65535u ? (-x) >> 31 : x);
> +    }
> +}
> +
> +int
> +main (void)
> +{
> +  int in[N];
> +  unsigned short out[N];
> +
> +  check_vect ();
> +
> +  for (int i = 0; i < N; ++i)
> +    in[i] = (i & 3) == 0 ? (-__INT_MAX__ - 1) : i * 12345 - 30000;
> +
> +  clip (out, in, N);
> +
> +#pragma GCC novector
> +  for (int i = 0; i < N; ++i)
> +    {
> +      int x = in[i];
> +      unsigned short ref;
> +
> +      if (x == (-__INT_MAX__ - 1) || x > 65535)
> +	ref = 65535;
> +      else if (x < 0)
> +	ref = 0;
> +      else
> +	ref = x;
> +      if (out[i] != ref)
> +	abort ();
> +    }
> +
> +  return 0;
> +}
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-1.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-1.c
> index 54f25e0ceaa..f5a9acec858 100644
> --- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-1.c
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-1.c
> @@ -16,6 +16,6 @@ clip_loop (uint8_t *res, int *x, int w)
>      res[i] = clip_uint8 (x[i]);
>  }
>  
> -/* { dg-final { scan-tree-dump-times ".SAT_TRUNC " 1 "optimized" } } */
> -/* { dg-final { scan-tree-dump-times "MAX_EXPR " 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times ".SAT_TRUNC " 2 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR " 2 "optimized" } } */
>  /* { dg-final { scan-assembler-times {vnclipu\.wi} 2 } } */
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-2.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-2.c
> index 9a880e0f67b..2208e954242 100644
> --- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-2.c
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-2.c
> @@ -1,5 +1,5 @@
>  /* { dg-do compile } */
> -/* { dg-options "-march=rv64gcv -mabi=lp64d -O3" } */
> +/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fdump-tree-optimized" } */
>  
>  #include <stdint.h>
>  
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c
> index d6b2ddd3f8d..5941b3b7543 100644
> --- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c
> @@ -1,5 +1,5 @@
>  /* { dg-do compile } */
> -/* { dg-options "-march=rv64gcv -mabi=lp64d -O3" } */
> +/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fdump-tree-optimized" } */
>  
>  #include <stdint.h>
>  
> @@ -16,6 +16,6 @@ clip_loop (uint8_t *res, int64_t *x, int w)
>      res[i] = clip_uint8 (x[i]);
>  }
>  
> -/* { dg-final { scan-tree-dump-times ".SAT_TRUNC " 1 "optimized" } } */
> -/* { dg-final { scan-tree-dump-times "MAX_EXPR " 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times ".SAT_TRUNC " 2 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR " 2 "optimized" } } */
>  /* { dg-final { scan-assembler-times {vnclipu\.wi} 3 } } */
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c
> index 4657e52f883..57cca4504ba 100644
> --- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c
> @@ -1,5 +1,5 @@
>  /* { dg-do compile } */
> -/* { dg-options "-march=rv64gcv -mabi=lp64d -O3" } */
> +/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fdump-tree-optimized" } */
>  
>  #include <stdint.h>
>  
>
  

Patch

diff --git a/gcc/match.pd b/gcc/match.pd
index 5777c833896..54cad1cd2bc 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -13372,6 +13372,43 @@  and,
  (BUILT_IN_CONSTANT_P (nop_convert@1 @0))
  (BUILT_IN_CONSTANT_P @0))
 
+/* Canonicalize a conditional signed narrow clip while the signed negation
+   has its original overflow semantics:
+
+     (NT) ((UT) X > NT_MAX ? (-X) >> (PREC - 1) : X)
+       -> (NT) MIN ((UT) MAX (X, 0), NT_MAX).  */
+(if (INTEGRAL_TYPE_P (type) && TYPE_UNSIGNED (type))
+ (simplify
+  (cond (gt (nop_convert@4 @0) INTEGER_CST@1)
+	(convert (rshift@5
+		  (nop_convert? (negate@3 (nop_convert? @0)))
+		  INTEGER_CST@2))
+	(convert @0))
+  (if (!TREE_SIDE_EFFECTS (@0)
+	&& !TYPE_UNSIGNED (TREE_TYPE (@0))
+	&& TYPE_UNSIGNED (TREE_TYPE (@4))
+	&& !TYPE_UNSIGNED (TREE_TYPE (@5))
+	&& TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@3))
+	&& !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@3)))
+   (with
+    {
+     tree utype = TREE_TYPE (@4);
+     unsigned itype_precision = TYPE_PRECISION (TREE_TYPE (@0));
+     unsigned otype_precision = TYPE_PRECISION (type);
+     wide_int trunc_max = wi::mask (otype_precision, false, itype_precision);
+     wide_int int_cst_1 = wi::to_wide (@1, itype_precision);
+     wide_int int_cst_2 = wi::to_wide (@2, itype_precision);
+     wide_int shift_amount = wi::uhwi (itype_precision - 1,
+				  itype_precision);
+    }
+    (if (otype_precision < itype_precision
+	 && wi::eq_p (trunc_max, int_cst_1)
+	 && wi::eq_p (int_cst_2, shift_amount))
+     (convert (min:utype
+		(convert:utype
+		 (max @0 { build_zero_cst (TREE_TYPE (@0)); }))
+		@1)))))))
+
 #if GIMPLE
 
 /* Include the saturation alu match patterns.  */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr103771.c b/gcc/testsuite/gcc.dg/tree-ssa/pr103771.c
index 8061e2df79e..b3dde923281 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr103771.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr103771.c
@@ -1,6 +1,7 @@ 
 /* { dg-do compile } */
-/* { dg-options "-O3 -fdump-tree-phiopt1-details" } */
-/* { dg-final { scan-tree-dump-times "changed to factor operation out from COND_EXPR." 1 "phiopt1" } } */
+/* { dg-options "-O3 -fdump-tree-gimple" } */
+/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "gimple" } } */
 
 typedef unsigned char uint8_t;
 
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr127166-3.c b/gcc/testsuite/gcc.dg/tree-ssa/pr127166-3.c
new file mode 100644
index 00000000000..266b0aac75a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr127166-3.c
@@ -0,0 +1,15 @@ 
+/* PR tree-optimization/127166 */
+/* { dg-do compile } */
+/* { dg-require-effective-target int32 } */
+/* { dg-options "-O2 -fsanitize=signed-integer-overflow" } */
+/* { dg-additional-options "-fdump-tree-optimized" } */
+
+unsigned short
+f (int x)
+{
+  return ((unsigned int) x > 65535u ? (-x) >> 31 : x);
+}
+
+/* Keep the conditional signed negation so that it is checked at runtime.  */
+/* { dg-final { scan-tree-dump-not "MAX_EXPR|MIN_EXPR" "optimized" } } */
+/* { dg-final { scan-tree-dump {\.UBSAN_CHECK_SUB} "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr127166.c b/gcc/testsuite/gcc.dg/tree-ssa/pr127166.c
new file mode 100644
index 00000000000..9bf89246dba
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr127166.c
@@ -0,0 +1,53 @@ 
+/* PR tree-optimization/127166 */
+/* { dg-do compile } */
+/* { dg-require-effective-target int32 } */
+/* { dg-options "-O2 -fdump-tree-gimple -fdump-tree-phiopt2" } */
+
+unsigned short
+signed_clip (int x)
+{
+  return ((unsigned int) x > 65535u ? (-x) >> 31 : x);
+}
+
+unsigned short
+unsigned_clip (int x)
+{
+  return ((unsigned int) x > 65535u
+	  ? (int) (-(unsigned int) x) >> 31 : x);
+}
+
+unsigned short
+signed_split_clip (int x)
+{
+  int neg = -x;
+  int sign = neg >> 31;
+  unsigned short high = sign;
+
+  return ((unsigned int) x > 65535u ? high : x);
+}
+
+unsigned short
+unsigned_split_clip (int x)
+{
+  unsigned int ux = x;
+  unsigned int neg = -ux;
+  int sign = (int) neg >> 31;
+  unsigned short high = sign;
+
+  return (ux > 65535u ? high : x);
+}
+
+volatile int v;
+
+unsigned short
+volatile_clip (void)
+{
+  return ((unsigned int) v > 65535u ? (-v) >> 31 : v);
+}
+
+/* The direct signed form is canonicalized in GENERIC.  The split signed form
+   is canonicalized in GIMPLE before loop if-conversion.  */
+/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "gimple" } } */
+/* { dg-final { scan-tree-dump-times "MAX_EXPR" 2 "phiopt2" } } */
+/* { dg-final { scan-tree-dump-times "MIN_EXPR" 2 "phiopt2" } } */
diff --git a/gcc/testsuite/gcc.dg/vect/pr127166.c b/gcc/testsuite/gcc.dg/vect/pr127166.c
new file mode 100644
index 00000000000..5bc59ad3769
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr127166.c
@@ -0,0 +1,50 @@ 
+/* PR tree-optimization/127166 */
+/* { dg-additional-options "-fwrapv" } */
+/* { dg-require-effective-target int32 } */
+/* { dg-require-effective-target vect_int } */
+
+#include "tree-vect.h"
+
+#define N 64
+
+__attribute__ ((noipa)) void
+clip (unsigned short *__restrict out, const int *__restrict in, int n)
+{
+  for (int i = 0; i < n; ++i)
+    {
+      int x = in[i];
+      out[i] = ((unsigned int) x > 65535u ? (-x) >> 31 : x);
+    }
+}
+
+int
+main (void)
+{
+  int in[N];
+  unsigned short out[N];
+
+  check_vect ();
+
+  for (int i = 0; i < N; ++i)
+    in[i] = (i & 3) == 0 ? (-__INT_MAX__ - 1) : i * 12345 - 30000;
+
+  clip (out, in, N);
+
+#pragma GCC novector
+  for (int i = 0; i < N; ++i)
+    {
+      int x = in[i];
+      unsigned short ref;
+
+      if (x == (-__INT_MAX__ - 1) || x > 65535)
+	ref = 65535;
+      else if (x < 0)
+	ref = 0;
+      else
+	ref = x;
+      if (out[i] != ref)
+	abort ();
+    }
+
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-1.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-1.c
index 54f25e0ceaa..f5a9acec858 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-1.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-1.c
@@ -16,6 +16,6 @@  clip_loop (uint8_t *res, int *x, int w)
     res[i] = clip_uint8 (x[i]);
 }
 
-/* { dg-final { scan-tree-dump-times ".SAT_TRUNC " 1 "optimized" } } */
-/* { dg-final { scan-tree-dump-times "MAX_EXPR " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times ".SAT_TRUNC " 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "MAX_EXPR " 2 "optimized" } } */
 /* { dg-final { scan-assembler-times {vnclipu\.wi} 2 } } */
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-2.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-2.c
index 9a880e0f67b..2208e954242 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-2.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-2.c
@@ -1,5 +1,5 @@ 
 /* { dg-do compile } */
-/* { dg-options "-march=rv64gcv -mabi=lp64d -O3" } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fdump-tree-optimized" } */
 
 #include <stdint.h>
 
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c
index d6b2ddd3f8d..5941b3b7543 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c
@@ -1,5 +1,5 @@ 
 /* { dg-do compile } */
-/* { dg-options "-march=rv64gcv -mabi=lp64d -O3" } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fdump-tree-optimized" } */
 
 #include <stdint.h>
 
@@ -16,6 +16,6 @@  clip_loop (uint8_t *res, int64_t *x, int w)
     res[i] = clip_uint8 (x[i]);
 }
 
-/* { dg-final { scan-tree-dump-times ".SAT_TRUNC " 1 "optimized" } } */
-/* { dg-final { scan-tree-dump-times "MAX_EXPR " 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times ".SAT_TRUNC " 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "MAX_EXPR " 2 "optimized" } } */
 /* { dg-final { scan-assembler-times {vnclipu\.wi} 3 } } */
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c
index 4657e52f883..57cca4504ba 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c
@@ -1,5 +1,5 @@ 
 /* { dg-do compile } */
-/* { dg-options "-march=rv64gcv -mabi=lp64d -O3" } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fdump-tree-optimized" } */
 
 #include <stdint.h>