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[LivePhysRegs] Preserve pristine regs in blocks with no successors.

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One common source of blocks with no successors is calls to noreturn
functions; we want to preserve pristine registers in case they throw an
exception.

The whole pristine register thing is messy (we should really prefer to
explicitly model registers), but this fills a hole in the model for now.

Fixes https://bugs.llvm.org/show_bug.cgi?id=36073.

Differential Revision: https://reviews.llvm.org/D42509

llvm-svn: 323559
This commit is contained in:
Eli Friedman 2018-01-26 20:23:00 +00:00
parent 1c3f5cf849
commit 844738750a
2 changed files with 49 additions and 2 deletions
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4
lib/CodeGen/LivePhysRegs.cpp
View File

@ -225,10 +225,10 @@ void LivePhysRegs::addLiveOutsNoPristines(const MachineBasicBlock &MBB) {
void LivePhysRegs::addLiveOuts(const MachineBasicBlock &MBB) {
const MachineFunction &MF = *MBB.getParent();
if (!MBB.succ_empty()) {
if (!MBB.isReturnBlock()) {
addPristines(MF);
addLiveOutsNoPristines(MBB);
} else if (MBB.isReturnBlock()) {
} else {
// For the return block: Add all callee saved registers.
const MachineFrameInfo &MFI = MF.getFrameInfo();
if (MFI.isCalleeSavedInfoValid())

47
test/CodeGen/Thumb/stm-scavenging.ll Normal file
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@ -0,0 +1,47 @@
; RUN: llc < %s | FileCheck %s
target triple = "thumbv6---gnueabi"
; Use STM to save the three registers
; CHECK-LABEL: use_stm:
; CHECK: .save {r7, lr}
; CHECK: .setfp r7, sp
; CHECK: stm r3!, {r0, r1, r2}
; CHECK: bl throws_1
define void @use_stm(i32 %a, i32 %b, i32 %c, i32* %d) local_unnamed_addr noreturn "no-frame-pointer-elim"="true" {
entry:
%arrayidx = getelementptr inbounds i32, i32* %d, i32 2
store i32 %a, i32* %arrayidx, align 4
%arrayidx1 = getelementptr inbounds i32, i32* %d, i32 3
store i32 %b, i32* %arrayidx1, align 4
%arrayidx2 = getelementptr inbounds i32, i32* %d, i32 4
store i32 %c, i32* %arrayidx2, align 4
tail call void @throws_1(i32 %a, i32 %b, i32 %c) noreturn
unreachable
}
; Don't use STM: there is no available register to store
; the address. We could transform this with some extra math, but
; that currently isn't implemented.
; CHECK-LABEL: no_stm:
; CHECK: .save {r7, lr}
; CHECK: .setfp r7, sp
; CHECK: str r0,
; CHECK: str r1,
; CHECK: str r2,
; CHECK: bl throws_2
define void @no_stm(i32 %a, i32 %b, i32 %c, i32* %d) local_unnamed_addr noreturn "no-frame-pointer-elim"="true" {
entry:
%arrayidx = getelementptr inbounds i32, i32* %d, i32 2
store i32 %a, i32* %arrayidx, align 4
%arrayidx1 = getelementptr inbounds i32, i32* %d, i32 3
store i32 %b, i32* %arrayidx1, align 4
%arrayidx2 = getelementptr inbounds i32, i32* %d, i32 4
store i32 %c, i32* %arrayidx2, align 4
tail call void @throws_2(i32 %a, i32 %b, i32 %c, i32* %d) noreturn
unreachable
}
declare void @throws_1(i32, i32, i32) noreturn
declare void @throws_2(i32, i32, i32, i32*) noreturn