diff mbox series

Fix build for STORE_FLAG_VALUE<0 targets [PR118418]

Message ID mpty0zelfuf.fsf@arm.com
State Committed
Commit a1a14ce3c39c25fecf052ffde063fc0ecfc2ffa3
Headers
Series Fix build for STORE_FLAG_VALUE<0 targets [PR118418] |

Checks

Context Check Description
linaro-tcwg-bot/tcwg_gcc_build--master-arm fail Patch failed to apply
linaro-tcwg-bot/tcwg_gcc_build--master-aarch64 fail Patch failed to apply

Commit Message

Richard Sandiford Jan. 13, 2025, 6:38 p.m. UTC 
  In g:06c4cf398947b53b4bfc65752f9f879bb2d07924 I mishandled signed
comparisons of comparison results on STORE_FLAG_VALUE < 0 targets
(despite specifically referencing STORE_FLAG_VALUE in the commit
message).  There, (lt TRUE FALSE) is true, although (ltu FALSE TRUE)
still holds.

Things get messy with vector modes, and since those weren't the focus
of the original commit, it seemed better to punt on them for now.
However, punting means that this optimisation no longer feels like
a natural tail-call operation.  The patch therefore converts
"return simplify..." to the usual call-and-conditional-return pattern.

Bootstrapped & regression-tested on aarch64-linux-gnu.  Also tested
by build m68k-elf.  OK to install?

Richard


gcc/
	* simplify-rtx.cc (simplify_context::simplify_relational_operation_1):
	Take STORE_FLAG_VALUE into account when handling signed comparisons
	of comparison results.
---
 gcc/simplify-rtx.cc | 39 ++++++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 15 deletions(-)

Comments

Jakub Jelinek Jan. 13, 2025, 6:47 p.m. UTC | #1 
On Mon, Jan 13, 2025 at 06:38:00PM +0000, Richard Sandiford wrote:
> In g:06c4cf398947b53b4bfc65752f9f879bb2d07924 I mishandled signed
> comparisons of comparison results on STORE_FLAG_VALUE < 0 targets
> (despite specifically referencing STORE_FLAG_VALUE in the commit
> message).  There, (lt TRUE FALSE) is true, although (ltu FALSE TRUE)
> still holds.
> 
> Things get messy with vector modes, and since those weren't the focus
> of the original commit, it seemed better to punt on them for now.
> However, punting means that this optimisation no longer feels like
> a natural tail-call operation.  The patch therefore converts
> "return simplify..." to the usual call-and-conditional-return pattern.
> 
> Bootstrapped & regression-tested on aarch64-linux-gnu.  Also tested
> by build m68k-elf.  OK to install?
> 
> Richard
> 
> 
> gcc/

Missing
	PR target/118418
here

> 	* simplify-rtx.cc (simplify_context::simplify_relational_operation_1):
> 	Take STORE_FLAG_VALUE into account when handling signed comparisons
> 	of comparison results.

Otherwise LGTM.

	Jakub
diff mbox series

Patch

diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index 71c5d3c1b1b..dda8fc689e7 100644
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -6434,7 +6434,7 @@  simplify_context::simplify_relational_operation_1 (rtx_code code,
 	return simplify_gen_binary (AND, mode, XEXP (tmp, 0), const1_rtx);
     }
 
-  /* For two booleans A and B:
+  /* For two unsigned booleans A and B:
 
      A >  B == ~B & A
      A >= B == ~B | A
@@ -6443,20 +6443,29 @@  simplify_context::simplify_relational_operation_1 (rtx_code code,
      A == B == ~A ^ B (== ~B ^ A)
      A != B ==  A ^ B
 
-     simplify_logical_relational_operation checks whether A and B
-     are booleans.  */
-  if (code == GTU || code == GT)
-    return simplify_logical_relational_operation (AND, mode, op1, op0, true);
-  if (code == GEU || code == GE)
-    return simplify_logical_relational_operation (IOR, mode, op1, op0, true);
-  if (code == LTU || code == LT)
-    return simplify_logical_relational_operation (AND, mode, op0, op1, true);
-  if (code == LEU || code == LE)
-    return simplify_logical_relational_operation (IOR, mode, op0, op1, true);
-  if (code == EQ)
-    return simplify_logical_relational_operation (XOR, mode, op0, op1, true);
-  if (code == NE)
-    return simplify_logical_relational_operation (XOR, mode, op0, op1);
+     For signed comparisons, we have to take STORE_FLAG_VALUE into account,
+     with the rules above applying for positive STORE_FLAG_VALUE and with
+     the relations reversed for negative STORE_FLAG_VALUE.  */
+  if (is_a<scalar_int_mode> (cmp_mode)
+      && COMPARISON_P (op0)
+      && COMPARISON_P (op1))
+    {
+      rtx t = NULL_RTX;
+      if (code == GTU || code == (STORE_FLAG_VALUE > 0 ? GT : LT))
+	t = simplify_logical_relational_operation (AND, mode, op1, op0, true);
+      else if (code == GEU || code == (STORE_FLAG_VALUE > 0 ? GE : LE))
+	t = simplify_logical_relational_operation (IOR, mode, op1, op0, true);
+      else if (code == LTU || code == (STORE_FLAG_VALUE > 0 ? LT : GT))
+	t = simplify_logical_relational_operation (AND, mode, op0, op1, true);
+      else if (code == LEU || code == (STORE_FLAG_VALUE > 0 ? LE : GE))
+	t = simplify_logical_relational_operation (IOR, mode, op0, op1, true);
+      else if (code == EQ)
+	t = simplify_logical_relational_operation (XOR, mode, op0, op1, true);
+      else if (code == NE)
+	t = simplify_logical_relational_operation (XOR, mode, op0, op1);
+      if (t)
+	return t;
+    }
 
   return NULL_RTX;
 }