maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[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

llvm-svn: 359041
This commit is contained in:
Francis Visoiu Mistrih 2019-04-23 21:57:46 +00:00
parent eea9da5921
commit 1646851b87
2 changed files with 10 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
llvm/lib/CodeGen/CodeGenPrepare.cpp
View File

@ -2032,7 +2032,9 @@ bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB, bool &ModifiedDT
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) &&

17
llvm/test/CodeGen/X86/tailcall-cgp-dup.ll
View File

@ -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