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|
# In certain cases CodeGenPrepare folds a return instruction into
# the return block's predecessor blocks and subsequently deletes the return block.
# The purpose of this is to enable tail call optimization in the predecessor blocks.
# Removal of the return block also removes fake use instructions that were present
# in the return block, potentially causing debug information to be lost.
#
# The fix is to clone any fake use instructions that are not dominated by definitions
# in the return block itself into the predecessor blocks. This test enures that we do so.
#
# Generated from the following source with
# clang -fextend-variable-liveness -S -emit-llvm -O2 -mllvm -stop-before=codegenprepare -o test.mir test.c
#
# extern int f0();
# extern int f1();
#
# int foo(int i) {
# int temp = i;
# if (temp == 0)
# temp = f0();
# else
# temp = f1();
# return temp;
# }
#
# RUN: llc -run-pass=codegenprepare -mtriple=x86_64-unknown-linux -o - %s | FileCheck %s
#
# CHECK: define{{.*}}foo
# CHECK: if.then:
# CHECK-NEXT: call{{.*}}fake.use(i32 %i)
# CHECK-NEXT: tail call i32{{.*}}@f0
# CHECK-NEXT: ret
# CHECK: if.else:
# CHECK-NEXT: call{{.*}}fake.use(i32 %i)
# CHECK-NEXT: tail call i32{{.*}}@f1
# CHECK-NEXT: ret
--- |
define hidden i32 @foo(i32 %i) local_unnamed_addr optdebug {
entry:
%cmp = icmp eq i32 %i, 0
br i1 %cmp, label %if.then, label %if.else
if.then:
%call = tail call i32 (...) @f0()
br label %if.end
if.else:
%call1 = tail call i32 (...) @f1()
br label %if.end
if.end:
%temp.0 = phi i32 [ %call, %if.then ], [ %call1, %if.else ]
notail call void (...) @llvm.fake.use(i32 %temp.0)
notail call void (...) @llvm.fake.use(i32 %i)
ret i32 %temp.0
}
declare i32 @f0(...) local_unnamed_addr
declare i32 @f1(...) local_unnamed_addr
...
---
name: foo
alignment: 16
exposesReturnsTwice: false
legalized: false
regBankSelected: false
selected: false
failedISel: false
tracksRegLiveness: true
hasWinCFI: false
registers: []
liveins: []
frameInfo:
isFrameAddressTaken: false
isReturnAddressTaken: false
hasStackMap: false
hasPatchPoint: false
stackSize: 0
offsetAdjustment: 0
maxAlignment: 1
adjustsStack: false
hasCalls: false
stackProtector: ''
maxCallFrameSize: 4294967295
cvBytesOfCalleeSavedRegisters: 0
hasOpaqueSPAdjustment: false
hasVAStart: false
hasMustTailInVarArgFunc: false
localFrameSize: 0
savePoint: ''
restorePoint: ''
fixedStack: []
stack: []
callSites: []
constants: []
machineFunctionInfo: {}
body: |
...
|
