dmgreen created this revision.
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The TC_RETURN/TCRETURNdi under Arm does not currently add the register-mask operand when tail folding, which leads to the register (like LR) not being 'used' by the return. This changes the code to unconditionally set the register mask on the call, as opposed to skipping it for tail calls.
I don't believe this will currently alter any codegen, but should glue things together better post-frame lowering. It matches the AArch64 code better, but I don't know this code very well.
https://reviews.llvm.org/D125906
Files:
llvm/lib/Target/ARM/ARMISelLowering.cpp
llvm/test/CodeGen/ARM/dbg-tcreturn.ll
Index: llvm/test/CodeGen/ARM/dbg-tcreturn.ll
===================================================================
--- llvm/test/CodeGen/ARM/dbg-tcreturn.ll
+++ llvm/test/CodeGen/ARM/dbg-tcreturn.ll
@@ -12,7 +12,7 @@
; CHECK-NEXT: $r0 = COPY %0
; CHECK-NEXT: $r1 = COPY %1
; CHECK-NEXT: DBG_VALUE $noreg, $noreg, !13, !DIExpression(), debug-location !16
-; CHECK-NEXT: TCRETURNdi &__divsi3, 0, implicit $sp, implicit $r0, implicit $r1
+; CHECK-NEXT: TCRETURNdi &__divsi3, 0, csr_ios, implicit $sp, implicit $r0, implicit $r1
define i32 @test(i32 %a1, i32 %a2) !dbg !5 {
entry:
Index: llvm/lib/Target/ARM/ARMISelLowering.cpp
===================================================================
--- llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -2786,25 +2786,23 @@
RegsToPass[i].second.getValueType()));
// Add a register mask operand representing the call-preserved registers.
- if (!isTailCall) {
- const uint32_t *Mask;
- const ARMBaseRegisterInfo *ARI = Subtarget->getRegisterInfo();
- if (isThisReturn) {
- // For 'this' returns, use the R0-preserving mask if applicable
- Mask = ARI->getThisReturnPreservedMask(MF, CallConv);
- if (!Mask) {
- // Set isThisReturn to false if the calling convention is not one that
- // allows 'returned' to be modeled in this way, so LowerCallResult does
- // not try to pass 'this' straight through
- isThisReturn = false;
- Mask = ARI->getCallPreservedMask(MF, CallConv);
- }
- } else
+ const uint32_t *Mask;
+ const ARMBaseRegisterInfo *ARI = Subtarget->getRegisterInfo();
+ if (isThisReturn) {
+ // For 'this' returns, use the R0-preserving mask if applicable
+ Mask = ARI->getThisReturnPreservedMask(MF, CallConv);
+ if (!Mask) {
+ // Set isThisReturn to false if the calling convention is not one that
+ // allows 'returned' to be modeled in this way, so LowerCallResult does
+ // not try to pass 'this' straight through
+ isThisReturn = false;
Mask = ARI->getCallPreservedMask(MF, CallConv);
+ }
+ } else
+ Mask = ARI->getCallPreservedMask(MF, CallConv);
- assert(Mask && "Missing call preserved mask for calling convention");
- Ops.push_back(DAG.getRegisterMask(Mask));
- }
+ assert(Mask && "Missing call preserved mask for calling convention");
+ Ops.push_back(DAG.getRegisterMask(Mask));
if (InFlag.getNode())
Ops.push_back(InFlag);
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