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[WebAssembly] Fix unbalanced register stack code in the case of late DCE.

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Instructions can be DCE'd after the RegStackify pass. If the instruction which
would be the pop for what would be a push is removed, don't use a push.

llvm-svn: 258694
This commit is contained in:
Dan Gohman 2016-01-25 16:48:44 +00:00
parent d1cae1c975
commit d5075eb344
2 changed files with 5 additions and 5 deletions
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6
lib/Target/WebAssembly/WebAssemblyRegNumbering.cpp
View File

@ -92,6 +92,9 @@ bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
unsigned CurReg = MFI.getParams().size();
for (unsigned VRegIdx = 0; VRegIdx < NumVRegs; ++VRegIdx) {
unsigned VReg = TargetRegisterInfo::index2VirtReg(VRegIdx);
// Skip unused registers.
if (MRI.use_empty(VReg))
continue;
// Handle stackified registers.
if (MFI.isVRegStackified(VReg)) {
DEBUG(dbgs() << "VReg " << VReg << " -> WAReg "
@ -99,9 +102,6 @@ bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
MFI.setWAReg(VReg, INT32_MIN | NumStackRegs++);
continue;
}
// Skip unused registers.
if (MRI.use_empty(VReg))
continue;
if (MFI.getWAReg(VReg) == WebAssemblyFunctionInfo::UnusedReg) {
DEBUG(dbgs() << "VReg " << VReg << " -> WAReg " << CurReg << "\n");
MFI.setWAReg(VReg, CurReg++);

4
test/CodeGen/WebAssembly/cfg-stackify.ll
View File

@ -1176,9 +1176,9 @@ bb5:
; CHECK-NEXT: .LBB23_2:{{$}}
; CHECK-NEXT: end_loop{{$}}
; CHECK-NEXT: loop{{$}}
; CHECK-NEXT: i32.const $discard=, 0{{$}}
; CHECK-NEXT: i32.const $push1=, 0{{$}}
; CHECK-NEXT: i32.const $push2=, 0{{$}}
; CHECK-NEXT: br_if $pop2, 0{{$}}
; CHECK-NEXT: br_if $pop1, 0{{$}}
; CHECK-NEXT: end_loop{{$}}
; CHECK-NEXT: return{{$}}
define void @test14() {