[LLVMbugs] [Bug 5645] New: llvm fails to fold function to a constant when built with clang

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=5645

           Summary: llvm fails to fold function to a constant when built
                    with clang
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Scalar Optimizations
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: daniel at zuster.org
                CC: llvmbugs at cs.uiuc.edu


The f6() function in the attached .cpp file fails to fold to a constant when
compiled with clang. This is bad, and I'm optimistically assuming its the
backends fault. LLVM does manage to fold it down if it happens to inline it, so
I suspect its something to do with aliasing on the alloca.
--
ddunbar at ozzy:tmp$ llvm-gcc -flto -S -O3 -o - t.cpp
; ModuleID = 't.cpp'
target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin10.0"

define i32 @_Z2f6v() nounwind ssp {
bb.i43:
  ret i32 1251552576
}
ddunbar at ozzy:tmp$ clang -flto -S -O3 -o - t.cpp
; ModuleID = 't.cpp'
target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin10.0"

%struct.TempTracker = type { i32, i32 }

define i32 @_Z2f6v() nounwind ssp {
while.body.i.i98.preheader:
  %tt = alloca %struct.TempTracker, align 4       ; <%struct.TempTracker*>
[#uses=2]
  %tmp.i = getelementptr inbounds %struct.TempTracker* %tt, i64 0, i32 0 ;
<i32*> [#uses=5]
  %tmp9.i152 = getelementptr inbounds %struct.TempTracker* %tt, i64 0, i32 1 ;
<i32*> [#uses=5]
  store i32 3, i32* %tmp.i
  store i32 2, i32* %tmp9.i152
  br label %while.body.i.i98

while.body.i.i98:                                 ; preds =
%while.body.i.i98.preheader, %while.body.i.i98
  %indvar.i.i93 = phi i32 [ %indvar.next.i.i96, %while.body.i.i98 ], [ 0,
%while.body.i.i98.preheader ] ; <i32> [#uses=1]
  %Val.06.i.i94 = phi i32 [ %mul.i.i95, %while.body.i.i98 ], [ 1,
%while.body.i.i98.preheader ] ; <i32> [#uses=2]
  %mul.i.i95 = mul i32 %Val.06.i.i94, 7           ; <i32> [#uses=1]
  %indvar.next.i.i96 = add i32 %indvar.i.i93, 1   ; <i32> [#uses=2]
  %exitcond = icmp eq i32 %indvar.next.i.i96, 2   ; <i1> [#uses=1]
  br i1 %exitcond, label %while.body.i.i74.preheader, label %while.body.i.i98

while.body.i.i74.preheader:                       ; preds = %while.body.i.i98
  %phitmp = mul i32 %Val.06.i.i94, 21             ; <i32> [#uses=2]
  store i32 %phitmp, i32* %tmp.i
  store i32 3, i32* %tmp9.i152
  br label %while.body.i.i74

while.body.i.i74:                                 ; preds =
%while.body.i.i74.preheader, %while.body.i.i74
  %indvar.i.i69 = phi i32 [ %indvar.next.i.i72, %while.body.i.i74 ], [ 0,
%while.body.i.i74.preheader ] ; <i32> [#uses=1]
  %Val.06.i.i70 = phi i32 [ %mul.i.i71, %while.body.i.i74 ], [ 1,
%while.body.i.i74.preheader ] ; <i32> [#uses=1]
  %mul.i.i71 = mul i32 %Val.06.i.i70, 11          ; <i32> [#uses=2]
  %indvar.next.i.i72 = add i32 %indvar.i.i69, 1   ; <i32> [#uses=2]
  %exitcond408 = icmp eq i32 %indvar.next.i.i72, 3 ; <i1> [#uses=1]
  br i1 %exitcond408, label %while.body.i.i50.preheader, label
%while.body.i.i74

while.body.i.i50.preheader:                       ; preds = %while.body.i.i74
  %mul.i79 = mul i32 %phitmp, %mul.i.i71          ; <i32> [#uses=2]
  store i32 %mul.i79, i32* %tmp.i
  store i32 4, i32* %tmp9.i152
  br label %while.body.i.i50

while.body.i.i50:                                 ; preds =
%while.body.i.i50.preheader, %while.body.i.i50
  %indvar.i.i45 = phi i32 [ %indvar.next.i.i48, %while.body.i.i50 ], [ 0,
%while.body.i.i50.preheader ] ; <i32> [#uses=1]
  %Val.06.i.i46 = phi i32 [ %mul.i.i47, %while.body.i.i50 ], [ 1,
%while.body.i.i50.preheader ] ; <i32> [#uses=1]
  %mul.i.i47 = mul i32 %Val.06.i.i46, 5           ; <i32> [#uses=2]
  %indvar.next.i.i48 = add i32 %indvar.i.i45, 1   ; <i32> [#uses=2]
  %exitcond410 = icmp eq i32 %indvar.next.i.i48, 4 ; <i1> [#uses=1]
  br i1 %exitcond410, label %while.body.i.i24.preheader, label
%while.body.i.i50

while.body.i.i24.preheader:                       ; preds = %while.body.i.i50
  %mul.i55 = mul i32 %mul.i79, %mul.i.i47         ; <i32> [#uses=2]
  store i32 %mul.i55, i32* %tmp.i
  store i32 5, i32* %tmp9.i152
  br label %while.body.i.i24

while.body.i.i24:                                 ; preds =
%while.body.i.i24.preheader, %while.body.i.i24
  %indvar.i.i19 = phi i32 [ %indvar.next.i.i22, %while.body.i.i24 ], [ 0,
%while.body.i.i24.preheader ] ; <i32> [#uses=1]
  %Val.06.i.i20 = phi i32 [ %mul.i.i21, %while.body.i.i24 ], [ 1,
%while.body.i.i24.preheader ] ; <i32> [#uses=1]
  %mul.i.i21 = mul i32 %Val.06.i.i20, 13          ; <i32> [#uses=2]
  %indvar.next.i.i22 = add i32 %indvar.i.i19, 1   ; <i32> [#uses=2]
  %exitcond412 = icmp eq i32 %indvar.next.i.i22, 5 ; <i1> [#uses=1]
  br i1 %exitcond412, label %while.body.i.i.preheader, label %while.body.i.i24

while.body.i.i.preheader:                         ; preds = %while.body.i.i24
  %mul.i29 = mul i32 %mul.i55, %mul.i.i21         ; <i32> [#uses=2]
  store i32 %mul.i29, i32* %tmp.i
  store i32 6, i32* %tmp9.i152
  br label %while.body.i.i

while.body.i.i:                                   ; preds =
%while.body.i.i.preheader, %while.body.i.i
  %indvar.i.i = phi i32 [ %indvar.next.i.i, %while.body.i.i ], [ 0,
%while.body.i.i.preheader ] ; <i32> [#uses=1]
  %Val.06.i.i = phi i32 [ %mul.i.i, %while.body.i.i ], [ 1,
%while.body.i.i.preheader ] ; <i32> [#uses=1]
  %mul.i.i = shl i32 %Val.06.i.i, 1               ; <i32> [#uses=2]
  %indvar.next.i.i = add i32 %indvar.i.i, 1       ; <i32> [#uses=2]
  %exitcond414 = icmp eq i32 %indvar.next.i.i, 6  ; <i1> [#uses=1]
  br i1 %exitcond414, label %_ZN1AD1Ev.exit, label %while.body.i.i

_ZN1AD1Ev.exit:                                   ; preds = %while.body.i.i
  %mul.i = mul i32 %mul.i29, %mul.i.i             ; <i32> [#uses=1]
  ret i32 %mul.i
}
ddunbar at ozzy:tmp$
 --


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