| Message ID | 87r3vbuecf.fsf@codesourcery.com |
|---|---|
| State | New |
| Headers | show |
On Sun, 4 Jan 2015, Yao Qi wrote: > I did the tests with the following options on both bare metal and linux > targets, > > -mabi=64 > -mabi=32 > -mabi=32 -mips16 > -mabi=32 -mmicromips > > and test this on bare metal target only, > > -mabi=32 -mips16 -mflip-mips16 > > instructions bal jal jals and jalx are generated in these combinations. Hmm, JALR used with `-mabi=64' on Linux must have been relaxed to BAL by the linker then; this will happen for in-range calls to a location within the same binary image when requested by the R_MIPS_JALR relocation, produced by GCC automatically where applicable. This is controlled with `-mrelax-pic-calls', so you should still see JALR on n64 Linux with: -mabi=64 -mno-relax-pic-calls You should also see JALR and possibly JALRC on MIPS16 Linux with: -mabi=32 -mips16 -mno-plt where no corresponding branch instruction to relax to is available. And you might see JALRS on microMIPS Linux with: -mabi=32 -mmicromips -mno-plt but I don't think you need to test these unless you really want to. I think BALS would only be observed if JALRS was relaxed, but this linker optimisation is missing. We should expect it to be corrected sometime though and be flexible on matching so that we don't have to update the test case again when other parts of the toolchain are updated. Thanks for the tests you ran, these are enough as far as I am concerned. > diff --git a/gdb/testsuite/gdb.trace/entry-values.exp b/gdb/testsuite/gdb.trace/entry-values.exp > index 6bb0514..50e9636 100644 > --- a/gdb/testsuite/gdb.trace/entry-values.exp > +++ b/gdb/testsuite/gdb.trace/entry-values.exp > @@ -43,6 +43,19 @@ if { [istarget "arm*-*-*"] || [istarget "aarch64*-*-*"] } { > set call_insn "brasl" > } elseif { [istarget "powerpc*-*-*"] } { > set call_insn "bl" > +} elseif { [istarget "mips*-*-*"] } { > + # Skip the delay slot after jump or branch instruction if it has. > + # > + # JUMP (or BRANCH) foo > + # insn1 > + # insn2 > + # > + # All the jump or branch instructions except jalrc (jal, jals, jalx, > + # jalr, jalrs, bal, bals) have the delay slot, so program goes to > + # insn2 when it returns from foo. How about: # Skip the delay slot after the instruction used to make a call # (which can be a jump or a branch) if it has one. # # JUMP (or BRANCH) foo # insn1 # insn2 # # Most MIPS instructions used to make calls have a delay slot. # These include JAL, JALS, JALX, JALR, JALRS, BAL and BALS. # In this case the program continues from `insn2' when `foo' # returns. The only exception is JALRC, in which case execution # resumes from `insn1' instead. ? Overall I'd prefer MIPS instructions to be spelled out capitalised in our documentation for consistency with hardware documentation. This makes them more prominent in text and also avoids confusing them with common words such as in `AND' vs `and'. The only exception are quoted pieces of assembly code where the language specifies mnemonics as lowercase strings. > If it is jalrc, set > + # RETURNED_FROM_FOO to insn1, otherwise set RETURNED_FROM_FOO to > + # insn2. > + set call_insn {jalrc|[jb]al[sxr]*[ \t][^\r\n]+\r\n} OK, this should work. I have a minor nit yet: `[sxr]?' will be more accurate than `[sxr]*', you want to see the letter at most once. The former regexp will likely interpret faster too. I'm fine with your change with these updates applied, or please feel free to post another proposal if you disagree with any of my suggestions and want to discuss them further. Thanks for your contribution. Maciej
"Maciej W. Rozycki" <macro@linux-mips.org> writes: > Overall I'd prefer MIPS instructions to be spelled out capitalised in our > documentation for consistency with hardware documentation. This makes > them more prominent in text and also avoids confusing them with common > words such as in `AND' vs `and'. The only exception are quoted pieces of > assembly code where the language specifies mnemonics as lowercase strings. > OK, that is fine to me. >> If it is jalrc, set >> + # RETURNED_FROM_FOO to insn1, otherwise set RETURNED_FROM_FOO to >> + # insn2. >> + set call_insn {jalrc|[jb]al[sxr]*[ \t][^\r\n]+\r\n} > > OK, this should work. I have a minor nit yet: `[sxr]?' will be more > accurate than `[sxr]*', you want to see the letter at most once. The > former regexp will likely interpret faster too. We want to match JALRS, so [sxr]* is needed here.
On Thu, 8 Jan 2015, Yao Qi wrote: > >> If it is jalrc, set > >> + # RETURNED_FROM_FOO to insn1, otherwise set RETURNED_FROM_FOO to > >> + # insn2. > >> + set call_insn {jalrc|[jb]al[sxr]*[ \t][^\r\n]+\r\n} > > > > OK, this should work. I have a minor nit yet: `[sxr]?' will be more > > accurate than `[sxr]*', you want to see the letter at most once. The > > former regexp will likely interpret faster too. > > We want to match JALRS, so [sxr]* is needed here. Fair enough, the pattern matches more than necessary, but there are no MIPS instructions it would match that it shouldn't, so let's keep your proposal as it is for simplicity. I have no further concerns, thanks for your work and for getting through this review. Maciej
diff --git a/gdb/testsuite/gdb.trace/entry-values.exp b/gdb/testsuite/gdb.trace/entry-values.exp index 6bb0514..50e9636 100644 --- a/gdb/testsuite/gdb.trace/entry-values.exp +++ b/gdb/testsuite/gdb.trace/entry-values.exp @@ -43,6 +43,19 @@ if { [istarget "arm*-*-*"] || [istarget "aarch64*-*-*"] } { set call_insn "brasl" } elseif { [istarget "powerpc*-*-*"] } { set call_insn "bl" +} elseif { [istarget "mips*-*-*"] } { + # Skip the delay slot after jump or branch instruction if it has. + # + # JUMP (or BRANCH) foo + # insn1 + # insn2 + # + # All the jump or branch instructions except jalrc (jal, jals, jalx, + # jalr, jalrs, bal, bals) have the delay slot, so program goes to + # insn2 when it returns from foo. If it is jalrc, set + # RETURNED_FROM_FOO to insn1, otherwise set RETURNED_FROM_FOO to + # insn2. + set call_insn {jalrc|[jb]al[sxr]*[ \t][^\r\n]+\r\n} } else { set call_insn "call" }