[llvm] r359041 - [CGP] Look through bitcasts when duplicating returns for tail calls
Francis Visoiu Mistrih via llvm-commits
llvm-commits at lists.llvm.org
Tue Apr 23 14:57:46 PDT 2019
Author: thegameg
Date: Tue Apr 23 14:57:46 2019
New Revision: 359041
URL: http://llvm.org/viewvc/llvm-project?rev=359041&view=rev
Log:
[CGP] Look through bitcasts when duplicating returns for tail calls
The simple case of:
```
int *callee();
void *caller(void *a) {
if (a == NULL)
return callee();
return a;
}
```
would generate a regular call instead of a tail call because we don't
look through the bitcast of the call to `callee` when duplicating the
return blocks.
Differential Revision: https://reviews.llvm.org/D60837
Modified:
llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
llvm/trunk/test/CodeGen/X86/tailcall-cgp-dup.ll
Modified: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp?rev=359041&r1=359040&r2=359041&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp Tue Apr 23 14:57:46 2019
@@ -2032,7 +2032,9 @@ bool CodeGenPrepare::dupRetToEnableTailC
SmallVector<CallInst*, 4> TailCalls;
if (PN) {
for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
- CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I));
+ // Look through bitcasts.
+ Value *IncomingVal = PN->getIncomingValue(I)->stripPointerCasts();
+ CallInst *CI = dyn_cast<CallInst>(IncomingVal);
// Make sure the phi value is indeed produced by the tail call.
if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
TLI->mayBeEmittedAsTailCall(CI) &&
Modified: llvm/trunk/test/CodeGen/X86/tailcall-cgp-dup.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/tailcall-cgp-dup.ll?rev=359041&r1=359040&r2=359041&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/tailcall-cgp-dup.ll (original)
+++ llvm/trunk/test/CodeGen/X86/tailcall-cgp-dup.ll Tue Apr 23 14:57:46 2019
@@ -118,21 +118,18 @@ define i8* @f_ret8(i8* %obj) nounwind {
; OPT: if.then:
; OPT-NEXT: [[PTR:%.*]] = tail call i32* @g_ret32()
; OPT-NEXT: [[CASTED:%.*]] = bitcast i32* [[PTR]] to i8*
-; OPT-NEXT: br label [[RETURN]]
+; OPT-NEXT: ret i8* [[CASTED]]
; OPT: return:
-; OPT-NEXT: [[RETVAL:%.*]] = phi i8* [ [[CASTED]], [[IF_THEN]] ], [ [[OBJ]], [[ENTRY:%.*]] ]
-; OPT-NEXT: ret i8* [[RETVAL]]
+; OPT-NEXT: ret i8* [[OBJ]]
;
; CHECK-LABEL: f_ret8:
; CHECK: ## %bb.0: ## %entry
-; CHECK-NEXT: movq %rdi, %rax
; CHECK-NEXT: testq %rdi, %rdi
-; CHECK-NEXT: je LBB3_2
-; CHECK-NEXT: ## %bb.1: ## %if.then
-; CHECK-NEXT: pushq %rax
-; CHECK-NEXT: callq _g_ret32
-; CHECK-NEXT: addq $8, %rsp
-; CHECK-NEXT: LBB3_2: ## %return
+; CHECK-NEXT: je LBB3_1
+; CHECK-NEXT: ## %bb.2: ## %if.then
+; CHECK-NEXT: jmp _g_ret32 ## TAILCALL
+; CHECK-NEXT: LBB3_1: ## %return
+; CHECK-NEXT: movq %rdi, %rax
; CHECK-NEXT: retq
entry:
%cmp = icmp eq i8* %obj, null
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