[CodeGen] Avoid handling DBG_VALUE in the LivePhysRegs (addUses,removeDefs,stepForward)
Summary:
This patch prevents DBG_VALUE instructions from influencing
LivePhysRegs::stepBackwards and stepForwards. In at least one case,
specifically branch folding, the stepBackwards logic was having an
influence on code generation. The result was that certain code
compiled with '-g -O2' would differ from that compiled with '-O2'
alone. It seems that the original logic, accounting for DBG_VALUE,
was influencing the placement of an IMPLICIT_DEF which had a later
impact on how blocks were processed in branch folding.
Reviewers: kparzysz, MatzeB
Reviewed By: kparzysz
Subscribers: bjope, llvm-commits
Tags: #debug-info
Differential Revision: https://reviews.llvm.org/D43850
llvm-svn: 327862
diff --git a/llvm/lib/CodeGen/LivePhysRegs.cpp b/llvm/lib/CodeGen/LivePhysRegs.cpp
index 277212c..62ff696 100644
--- a/llvm/lib/CodeGen/LivePhysRegs.cpp
+++ b/llvm/lib/CodeGen/LivePhysRegs.cpp
@@ -44,7 +44,7 @@
void LivePhysRegs::removeDefs(const MachineInstr &MI) {
for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
if (O->isReg()) {
- if (!O->isDef())
+ if (!O->isDef() || O->isDebug())
continue;
unsigned Reg = O->getReg();
if (!TargetRegisterInfo::isPhysicalRegister(Reg))
@@ -58,7 +58,7 @@
/// Add uses to the set.
void LivePhysRegs::addUses(const MachineInstr &MI) {
for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
- if (!O->isReg() || !O->readsReg())
+ if (!O->isReg() || !O->readsReg() || O->isDebug())
continue;
unsigned Reg = O->getReg();
if (!TargetRegisterInfo::isPhysicalRegister(Reg))
@@ -85,7 +85,7 @@
SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> &Clobbers) {
// Remove killed registers from the set.
for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
- if (O->isReg()) {
+ if (O->isReg() && !O->isDebug()) {
unsigned Reg = O->getReg();
if (!TargetRegisterInfo::isPhysicalRegister(Reg))
continue;