[llvm] c79bc59 - [PowerPC][Bug] Fix Bug in Stack Frame Update Code
Stefan Pintilie via llvm-commits
llvm-commits at lists.llvm.org
Tue May 11 03:54:13 PDT 2021
Author: Stefan Pintilie
Date: 2021-05-11T05:54:07-05:00
New Revision: c79bc5942d0efd4740c7a6d36ad951c59ef3bc0e
URL: https://github.com/llvm/llvm-project/commit/c79bc5942d0efd4740c7a6d36ad951c59ef3bc0e
DIFF: https://github.com/llvm/llvm-project/commit/c79bc5942d0efd4740c7a6d36ad951c59ef3bc0e.diff
LOG: [PowerPC][Bug] Fix Bug in Stack Frame Update Code
The stack frame update code does not take into consideration spilling
to registers for callee saved registers. The option -ppc-enable-pe-vector-spills
turns on spilling to registers for callee saved registers and may expose a bug
in the code that moves a stack frame pointer update instruction.
Reviewed By: nemanjai, #powerpc
Differential Revision: https://reviews.llvm.org/D101366
Added:
llvm/test/CodeGen/PowerPC/stack_pointer_vec_spills.mir
Modified:
llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp b/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
index 5d53053216c81..0bebfc386b509 100644
--- a/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
@@ -733,6 +733,22 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF,
if (stackUpdateCanBeMoved(MF)) {
const std::vector<CalleeSavedInfo> &Info = MFI.getCalleeSavedInfo();
for (CalleeSavedInfo CSI : Info) {
+ // If the callee saved register is spilled to a register instead of the
+ // stack then the spill no longer uses the stack pointer.
+ // This can lead to two consequences:
+ // 1) We no longer need to update the stack because the function does not
+ // spill any callee saved registers to stack.
+ // 2) We have a situation where we still have to update the stack pointer
+ // even though some registers are spilled to other registers. In
+ // this case the current code moves the stack update to an incorrect
+ // position.
+ // In either case we should abort moving the stack update operation.
+ if (CSI.isSpilledToReg()) {
+ StackUpdateLoc = MBBI;
+ MovingStackUpdateDown = false;
+ break;
+ }
+
int FrIdx = CSI.getFrameIdx();
// If the frame index is not negative the callee saved info belongs to a
// stack object that is not a fixed stack object. We ignore non-fixed
@@ -1621,6 +1637,12 @@ void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
if (stackUpdateCanBeMoved(MF)) {
const std::vector<CalleeSavedInfo> & Info = MFI.getCalleeSavedInfo();
for (CalleeSavedInfo CSI : Info) {
+ // If the callee saved register is spilled to another register abort the
+ // stack update movement.
+ if (CSI.isSpilledToReg()) {
+ StackUpdateLoc = MBBI;
+ break;
+ }
int FrIdx = CSI.getFrameIdx();
// If the frame index is not negative the callee saved info belongs to a
// stack object that is not a fixed stack object. We ignore non-fixed
diff --git a/llvm/test/CodeGen/PowerPC/stack_pointer_vec_spills.mir b/llvm/test/CodeGen/PowerPC/stack_pointer_vec_spills.mir
new file mode 100644
index 0000000000000..b0615959d91c6
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/stack_pointer_vec_spills.mir
@@ -0,0 +1,41 @@
+# RUN: llc -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr9 \
+# RUN: -start-before=prologepilog -ppc-enable-pe-vector-spills \
+# RUN: -ppc-asm-full-reg-names -verify-machineinstrs %s -o - | FileCheck %s
+
+---
+name: MixedSpill
+alignment: 16
+tracksRegLiveness: true
+liveins:
+body: |
+ bb.0.entry:
+ $r14 = IMPLICIT_DEF
+ $f14 = IMPLICIT_DEF
+ $lr8 = IMPLICIT_DEF
+ BLR8 implicit undef $lr8, implicit undef $rm
+
+# CHECK-LABEL: MixedSpill
+# CHECK: stdu r1, -176(r1)
+# CHECK: stfd f14, 32(r1)
+# CHECK: mtvsrd vs32, r14
+# CHECK: lfd f14, 32(r1)
+# CHECK: addi r1, r1, 176
+# CHECK: blr
+...
+---
+name: NoStackUpdate
+alignment: 16
+tracksRegLiveness: true
+liveins:
+body: |
+ bb.0.entry:
+ $r14 = IMPLICIT_DEF
+ $f14 = IMPLICIT_DEF
+ BLR8 implicit undef $lr8, implicit undef $rm
+
+# CHECK-LABEL: NoStackUpdate
+# CHECK-NOT: stdu
+# CHECK: mtvsrd vs32, r14
+# CHECK: mfvsrd r14, vs32
+# CHECK: blr
+...
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