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SROA: Don't insert instructions before a PHI 

SROA may decide that it needs to insert a bitcast and would set it's
insertion point before a PHI.  This will create an invalid module
right quick.

Instead, choose the first insertion point in the basic block that holds
our PHI.

This fixes PR20822.

Differential Revision: http://reviews.llvm.org/D5141

llvm-svn: 216891
This commit is contained in:
David Majnemer 2014-09-01 21:20:14 +00:00
parent d2df50196f
commit d4cffcf073
2 changed files with 38 additions and 1 deletions
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5
llvm/lib/Transforms/Scalar/SROA.cpp
View File

@ -2708,7 +2708,10 @@ private:
// the old pointer, which necessarily must be in the right position to
// dominate the PHI.
IRBuilderTy PtrBuilder(IRB);
PtrBuilder.SetInsertPoint(OldPtr);
if (isa<PHINode>(OldPtr))
PtrBuilder.SetInsertPoint(OldPtr->getParent()->getFirstInsertionPt());
else
PtrBuilder.SetInsertPoint(OldPtr);
PtrBuilder.SetCurrentDebugLocation(OldPtr->getDebugLoc());
Value *NewPtr = getNewAllocaSlicePtr(PtrBuilder, OldPtr->getType());

34
llvm/test/Transforms/SROA/phi-and-select.ll
View File

@ -566,3 +566,37 @@ merge:
%4 = load float* %3, align 4
ret float %4
}
%struct.S = type { i32 }
; Verifies we fixed PR20822. We have a foldable PHI feeding a speculatable PHI
; which requires the rewriting of the speculated PHI to handle insertion
; when the incoming pointer is itself from a PHI node. We would previously
; insert a bitcast instruction *before* a PHI, producing an invalid module;
; make sure we insert *after* the first non-PHI instruction.
define void @PR20822() {
; CHECK-LABEL: @PR20822(
entry:
%f = alloca %struct.S, align 4
; CHECK: %[[alloca:.*]] = alloca
br i1 undef, label %if.end, label %for.cond
for.cond: ; preds = %for.cond, %entry
br label %if.end
if.end: ; preds = %for.cond, %entry
%f2 = phi %struct.S* [ %f, %entry ], [ %f, %for.cond ]
; CHECK: phi i32
; CHECK: %[[cast:.*]] = bitcast i32* %[[alloca]] to %struct.S*
phi i32 [ undef, %entry ], [ undef, %for.cond ]
br i1 undef, label %if.then5, label %if.then2
if.then2: ; preds = %if.end
br label %if.then5
if.then5: ; preds = %if.then2, %if.end
%f1 = phi %struct.S* [ undef, %if.then2 ], [ %f2, %if.end ]
; CHECK: phi {{.*}} %[[cast]]
store %struct.S undef, %struct.S* %f1, align 4
ret void
}