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Fix Sub-register Rewriting in Aggressive Anti-Dependence Breaker

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Previously, HandleLastUse would delete RegRef information for sub-registers
if they were dead even if their corresponding super-register were still live.

If the super-register were later renamed, then the definitions of the
sub-register would not be updated appropriately. This patch alters the
behavior so that RegInfo information for sub-registers is only deleted when
the sub-register and super-register are both dead.

This resolves PR26775. This is the mirror image of Hal's r227311 commit.

Author: Tom Jablin (tjablin)
Reviewers: kbarton uweigand nemanjai hfinkel

http://reviews.llvm.org/D18448

llvm-svn: 265097
This commit is contained in:
Chuang-Yu Cheng 2016-04-01 02:05:29 +00:00
parent e1ba9e8e87
commit 283d5efd78
2 changed files with 40 additions and 13 deletions
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29
lib/CodeGen/AggressiveAntiDepBreaker.cpp
View File

@ -312,19 +312,22 @@ void AggressiveAntiDepBreaker::HandleLastUse(unsigned Reg, unsigned KillIdx,
DEBUG(if (header) {
dbgs() << header << TRI->getName(Reg); header = nullptr; });
DEBUG(dbgs() << "->g" << State->GetGroup(Reg) << tag);
}
// Repeat for subregisters.
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
unsigned SubregReg = *SubRegs;
if (!State->IsLive(SubregReg)) {
KillIndices[SubregReg] = KillIdx;
DefIndices[SubregReg] = ~0u;
RegRefs.erase(SubregReg);
State->LeaveGroup(SubregReg);
DEBUG(if (header) {
dbgs() << header << TRI->getName(Reg); header = nullptr; });
DEBUG(dbgs() << " " << TRI->getName(SubregReg) << "->g" <<
State->GetGroup(SubregReg) << tag);
// Repeat for subregisters. Note that we only do this if the superregister
// was not live because otherwise, regardless whether we have an explicit
// use of the subregister, the subregister's contents are needed for the
// uses of the superregister.
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
unsigned SubregReg = *SubRegs;
if (!State->IsLive(SubregReg)) {
KillIndices[SubregReg] = KillIdx;
DefIndices[SubregReg] = ~0u;
RegRefs.erase(SubregReg);
State->LeaveGroup(SubregReg);
DEBUG(if (header) {
dbgs() << header << TRI->getName(Reg); header = nullptr; });
DEBUG(dbgs() << " " << TRI->getName(SubregReg) << "->g" <<
State->GetGroup(SubregReg) << tag);
}
}
}

24
test/CodeGen/PowerPC/aggressive-anti-dep-breaker-subreg.ll Normal file
View File

@ -0,0 +1,24 @@
; RUN: llc %s -mtriple=powerpc64-unknown-linux-gnu -O2 -o - -optimize-regalloc=false -regalloc=fast | FileCheck %s
declare void @func(i8*, i64, i64)
define void @test(i8* %context, i32** %elementArrayPtr, i32 %value) {
entry:
%cmp = icmp eq i32 %value, 0
br i1 %cmp, label %lreturn, label %lnext
lnext:
%elementArray = load i32*, i32** %elementArrayPtr, align 8
; CHECK: lwz [[LDREG:[0-9]+]], 124(1) # 4-byte Folded Reload
; CHECK: # implicit-def: %X[[TEMPREG:[0-9]+]]
%element = load i32, i32* %elementArray, align 4
; CHECK: mr [[TEMPREG]], [[LDREG]]
; CHECK: clrldi 4, [[TEMPREG]], 32
%element.ext = zext i32 %element to i64
%value.ext = zext i32 %value to i64
call void @func(i8* %context, i64 %value.ext, i64 %element.ext)
br label %lreturn
lreturn:
ret void
}