[RegAllocFast] Scan physcial reg definitions before assigning virtual reg definitions
When assigning the definitions of an instruction we were updating
the available registers while walking the definitions. Some of
those definitions may be from physical registers and thus, they are
not available for other definitions to take, but by the time we see
that we may have already assign these registers to another
virtual register.
Fix that by walking through all the definitions and mark as unavailable
the physical register definitions, then do the virtual register assignments.
PR41790
llvm-svn: 360278
diff --git a/llvm/lib/CodeGen/RegAllocFast.cpp b/llvm/lib/CodeGen/RegAllocFast.cpp
index c11ae9c..52502a4 100644
--- a/llvm/lib/CodeGen/RegAllocFast.cpp
+++ b/llvm/lib/CodeGen/RegAllocFast.cpp
@@ -1058,6 +1058,20 @@
}
// Third scan.
+ // Mark all physreg defs as used before allocating virtreg defs.
+ for (unsigned I = 0; I != DefOpEnd; ++I) {
+ const MachineOperand &MO = MI.getOperand(I);
+ if (!MO.isReg() || !MO.isDef() || !MO.getReg() || MO.isEarlyClobber())
+ continue;
+ unsigned Reg = MO.getReg();
+
+ if (!Reg || !TargetRegisterInfo::isPhysicalRegister(Reg) ||
+ !MRI->isAllocatable(Reg))
+ continue;
+ definePhysReg(MI, Reg, MO.isDead() ? regFree : regReserved);
+ }
+
+ // Fourth scan.
// Allocate defs and collect dead defs.
for (unsigned I = 0; I != DefOpEnd; ++I) {
const MachineOperand &MO = MI.getOperand(I);
@@ -1065,11 +1079,9 @@
continue;
unsigned Reg = MO.getReg();
- if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
- if (!MRI->isAllocatable(Reg)) continue;
- definePhysReg(MI, Reg, MO.isDead() ? regFree : regReserved);
+ // We have already dealt with phys regs in the previous scan.
+ if (TargetRegisterInfo::isPhysicalRegister(Reg))
continue;
- }
MCPhysReg PhysReg = defineVirtReg(MI, I, Reg, CopySrcReg);
if (setPhysReg(MI, MI.getOperand(I), PhysReg)) {
VirtDead.push_back(Reg);