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[SystemZ] Drop regstate of SELRMux operand in selectSLRMux(). #128555

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Merged
merged 2 commits into from
Feb 28, 2025
Merged

[SystemZ] Drop regstate of SELRMux operand in selectSLRMux(). #128555

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c1db6a6
Drop regstate of SELRMux operand.
JonPsson1 Feb 24, 2025
0975640
Use intersection of flags.
JonPsson1 Feb 27, 2025
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2 changes: 1 addition & 1 deletion llvm/lib/Target/SystemZ/SystemZPostRewrite.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -114,7 +114,7 @@ void SystemZPostRewrite::selectSELRMux(MachineBasicBlock &MBB,
if (Src1Reg == Src2Reg) {
BuildMI(*MBBI->getParent(), MBBI, MBBI->getDebugLoc(),
TII->get(SystemZ::COPY), DestReg)
.addReg(MBBI->getOperand(1).getReg(), getRegState(MBBI->getOperand(1)));
.addReg(MBBI->getOperand(1).getReg(), RegState::Renamable);
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@uweigand uweigand Feb 25, 2025

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Hard-coding the renamable looks odd to me. It may be correct now, but who knows what's going on after possible future changes?

Since the same register is present as both source operands, but with differing regstate flags, can't we simply use the intersection of the flags from the two operands here?

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@JonPsson1 JonPsson1 Feb 27, 2025

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ok - makes sense. Also added the verifier to the test so that in any possible case where there might be a flag that requires one of a set of other flags this would hopefully be reported.

MBBI->eraseFromParent();
return;
}
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2 changes: 1 addition & 1 deletion llvm/test/CodeGen/SystemZ/cond-move-10.mir
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Expand Up @@ -5,7 +5,7 @@
# CHECK: name: fun0
# CHECK: renamable $r1l = AHIMuxK killed renamable $r1l, -1, implicit-def dead $cc
# CHECK-NEXT: CHIMux renamable $r5h, 9, implicit-def $cc
# CHECK-NEXT: $r14h = COPY killed renamable $r1l
# CHECK-NEXT: $r14h = COPY renamable $r1l
---
name: fun0
tracksRegLiveness: true
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43 changes: 43 additions & 0 deletions llvm/test/CodeGen/SystemZ/cond-move-11.mir
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@@ -0,0 +1,43 @@
# RUN: llc -o - %s -mtriple=s390x-linux-gnu -mcpu=z15 -start-before=systemz-post-rewrite \
# RUN: -stop-after=machine-cp 2>&1 | FileCheck %s

# The chained SELRMux:es both has two operands with the same register but
# where one of the operands have been marked as undef (resulting from
# early-ifcvt). Check that the resulting COPY after machine-cp is from $r0l
# to $r2l.

# CHECK: name: fun0
# CHECK: $r2l = COPY $r0l
--- |

@Res = global i32 0, align 4
@Z = global i32 0, align 4
define signext i32 @fun0() { ret i32 0 }
...
---
name: fun0
tracksRegLiveness: true
body: |
bb.0:
successors: %bb.1(0x80000000)

renamable $r0l = LRL @Z :: (dereferenceable load (s32) from @Z)
renamable $r1l = LHIMux 1

bb.1:
successors: %bb.1(0x7c000000), %bb.2(0x04000000)
liveins: $r0l, $r1l

CHIMux renamable $r1l, 0, implicit-def $cc
renamable $r2l = SELRMux undef renamable $r0l, renamable $r0l, 14, 6, implicit $cc
renamable $r2l = SELRMux undef renamable $r2l, killed renamable $r2l, 14, 6, implicit $cc
BRC 14, 8, %bb.1, implicit killed $cc
J %bb.2

bb.2:
liveins: $r2l

STRL renamable $r2l, @Res :: (store (s32) into @Res)
renamable $r2d = LGFR killed renamable $r2l
Return implicit $r2d
...
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