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[SCCP] Can't go from overdefined to constant

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The fix for PR23999 made us mark loads of null as producing the constant
undef which upsets the lattice.  Instead, keep the load as "undefined".
This fixes PR26044.

llvm-svn: 257087
This commit is contained in:
David Majnemer 2016-01-07 19:25:39 +00:00
parent 5fb9cd1356
commit dce0498b16
2 changed files with 34 additions and 3 deletions
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6
lib/Transforms/Scalar/SCCP.cpp
View File

@ -1047,7 +1047,7 @@ void SCCPSolver::visitStoreInst(StoreInst &SI) {
// global, we can replace the load with the loaded constant value!
void SCCPSolver::visitLoadInst(LoadInst &I) {
// If this load is of a struct, just mark the result overdefined.
if (I.getType()->isStructTy())
if (I.getType()->isStructTy() || I.getType()->isMMXTy())
return markAnythingOverdefined(&I);
LatticeVal PtrVal = getValueState(I.getOperand(0));
@ -1061,9 +1061,9 @@ void SCCPSolver::visitLoadInst(LoadInst &I) {
Constant *Ptr = PtrVal.getConstant();
// load null -> null
// load null is undefined.
if (isa<ConstantPointerNull>(Ptr) && I.getPointerAddressSpace() == 0)
return markConstant(IV, &I, UndefValue::get(I.getType()));
return;
// Transform load (constant global) into the value loaded.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {

31
test/Transforms/IPConstantProp/PR26044.ll Normal file
View File

@ -0,0 +1,31 @@
; RUN: opt < %s -S -ipsccp | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define void @fn2() {
entry:
br label %if.end
for.cond1: ; preds = %if.end, %for.end
br i1 undef, label %if.end, label %if.end
if.end: ; preds = %lbl, %for.cond1
%e.2 = phi i32* [ undef, %entry ], [ null, %for.cond1 ], [ null, %for.cond1 ]
%0 = load i32, i32* %e.2, align 4
%call = call i32 @fn1(i32 %0)
br label %for.cond1
}
define internal i32 @fn1(i32 %p1) {
entry:
%tobool = icmp ne i32 %p1, 0
%cond = select i1 %tobool, i32 %p1, i32 %p1
ret i32 %cond
}
; CHECK-LABEL: define void @fn2(
; CHECK: call i32 @fn1(i32 undef)
; CHECK-LABEL: define internal i32 @fn1(
; CHECK:%[[COND:.*]] = select i1 undef, i32 undef, i32 undef
; CHECK: ret i32 %[[COND]]