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Fix PR5391: support early clobber physical register def tied with a use (ewwww)

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- A valno should be set HasRedefByEC if there is an early clobber def in the middle of its live ranges. It should not be set if the def of the valno is defined by an early clobber.
- If a physical register def is tied to an use and it's an early clobber, it just means the HasRedefByEC is set since it's still one continuous live range.
- Add a couple of missing checks for HasRedefByEC in the coalescer. In general, it should not coalesce a vr with a physical register if the physical register has a early clobber def somewhere. This is overly conservative but that's the price for using such a nasty inline asm "feature".


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90269 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2009-12-01 22:25:00 +00:00
parent 2a37b9c750
commit 9836a26da3
3 changed files with 50 additions and 4 deletions
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4
lib/CodeGen/LiveIntervalAnalysis.cpp
View File

@ -374,8 +374,6 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
// Value#0 is now defined by the 2-addr instruction.
OldValNo->def = RedefIndex;
OldValNo->setCopy(0);
if (MO.isEarlyClobber())
OldValNo->setHasRedefByEC(true);
// Add the new live interval which replaces the range for the input copy.
LiveRange LR(DefIndex, RedefIndex, ValNo);
@ -513,8 +511,6 @@ void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB,
if (mi->isRegTiedToUseOperand(DefIdx)) {
// Two-address instruction.
end = baseIndex.getDefIndex();
assert(!mi->getOperand(DefIdx).isEarlyClobber() &&
"Two address instruction is an early clobber?");
} else {
// Another instruction redefines the register before it is ever read.
// Then the register is essentially dead at the instruction that defines

12
lib/CodeGen/SimpleRegisterCoalescing.cpp
View File

@ -1938,6 +1938,10 @@ bool SimpleRegisterCoalescing::SimpleJoin(LiveInterval &LHS, LiveInterval &RHS){
if (Overlaps) {
// If we haven't already recorded that this value # is safe, check it.
if (!InVector(LHSIt->valno, EliminatedLHSVals)) {
// If it's re-defined by an early clobber somewhere in the live range,
// then conservatively abort coalescing.
if (LHSIt->valno->hasRedefByEC())
return false;
// Copy from the RHS?
if (!RangeIsDefinedByCopyFromReg(LHS, LHSIt, RHS.reg))
return false; // Nope, bail out.
@ -1977,6 +1981,10 @@ bool SimpleRegisterCoalescing::SimpleJoin(LiveInterval &LHS, LiveInterval &RHS){
// if coalescing succeeds. Just skip the liverange.
if (++LHSIt == LHSEnd) break;
} else {
// If it's re-defined by an early clobber somewhere in the live range,
// then conservatively abort coalescing.
if (LHSIt->valno->hasRedefByEC())
return false;
// Otherwise, if this is a copy from the RHS, mark it as being merged
// in.
if (RangeIsDefinedByCopyFromReg(LHS, LHSIt, RHS.reg)) {
@ -2316,6 +2324,10 @@ SimpleRegisterCoalescing::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS,
if (LHSValNoAssignments[I->valno->id] !=
RHSValNoAssignments[J->valno->id])
return false;
// If it's re-defined by an early clobber somewhere in the live range,
// then conservatively abort coalescing.
if (NewVNInfo[LHSValNoAssignments[I->valno->id]]->hasRedefByEC())
return false;
}
if (I->end < J->end) {

38
test/CodeGen/X86/2009-12-01-EarlyClobberBug.ll Normal file
View File

@ -0,0 +1,38 @@
; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
; pr5391
define void @t() nounwind ssp {
entry:
; CHECK: t:
; CHECK: movl %ecx, %eax
; CHECK: %eax = foo (%eax, %ecx)
%b = alloca i32 ; <i32*> [#uses=2]
%a = alloca i32 ; <i32*> [#uses=1]
%"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
%0 = load i32* %b, align 4 ; <i32> [#uses=1]
%1 = load i32* %b, align 4 ; <i32> [#uses=1]
%asmtmp = call i32 asm "$0 = foo ($1, $2)", "=&{ax},%0,r,~{dirflag},~{fpsr},~{flags}"(i32 %0, i32 %1) nounwind ; <i32> [#uses=1]
store i32 %asmtmp, i32* %a
br label %return
return: ; preds = %entry
ret void
}
define void @t2() nounwind ssp {
entry:
; CHECK: t2:
; CHECK: movl %eax, %ecx
; CHECK: %ecx = foo (%ecx, %eax)
%b = alloca i32 ; <i32*> [#uses=2]
%a = alloca i32 ; <i32*> [#uses=1]
%"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
%0 = load i32* %b, align 4 ; <i32> [#uses=1]
%1 = load i32* %b, align 4 ; <i32> [#uses=1]
%asmtmp = call i32 asm "$0 = foo ($1, $2)", "=&r,%0,r,~{dirflag},~{fpsr},~{flags}"(i32 %0, i32 %1) nounwind ; <i32> [#uses=1]
store i32 %asmtmp, i32* %a
br label %return
return: ; preds = %entry
ret void
}