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[InstCombine] don't assert that division-by-constant has been folded (PR30281) 

This is effectively a revert of:
https://reviews.llvm.org/rL280115

And this should fix
https://llvm.org/bugs/show_bug.cgi?id=30281:

llvm-svn: 280677
This commit is contained in:
Sanjay Patel 2016-09-05 23:38:22 +00:00
parent 46f9df5b71
commit eea2ef7862
2 changed files with 99 additions and 7 deletions
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13
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -1976,13 +1976,12 @@ Instruction *InstCombiner::foldICmpDivConstant(ICmpInst &Cmp,
if (!Cmp.isEquality() && DivIsSigned != Cmp.isSigned())
return nullptr;
// These constant divides should already be folded in InstSimplify.
assert(*C2 != 0 && "The ProdOV computation fails on divide by zero.");
assert(*C2 != 1 && "Funny cases with INT_MIN will fail.");
// This constant divide should already be folded in InstCombine.
assert(!(DivIsSigned && C2->isAllOnesValue()) &&
"The overflow computation will fail.");
// The ProdOV computation fails on divide by 0 and divide by -1. Cases with
// INT_MIN will also fail if the divisor is 1. Although folds of all these
// division-by-constant cases should be present, we can not assert that they
// have happened before we reach this icmp instruction.
if (*C2 == 0 || *C2 == 1 || (DivIsSigned && C2->isAllOnesValue()))
return nullptr;
// TODO: We could do all of the computations below using APInt.
Constant *CmpRHS = cast<Constant>(Cmp.getOperand(1));

93
llvm/test/Transforms/InstCombine/icmp-div-constant.ll Normal file
View File

@ -0,0 +1,93 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S | FileCheck %s
; PR30281 - https://llvm.org/bugs/show_bug.cgi?id=30281
; All of these tests contain foldable division-by-constant instructions, but we
; can't assert that those folds have occurred before we process the later icmp.
define i32 @icmp_div(i16 %a, i16 %c) {
; CHECK-LABEL: @icmp_div(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp eq i16 %a, 0
; CHECK-NEXT: br i1 [[TOBOOL]], label %then, label %exit
; CHECK: then:
; CHECK-NEXT: [[NOT_CMP:%.*]] = icmp eq i16 %c, 0
; CHECK-NEXT: [[PHITMP1:%.*]] = sext i1 [[NOT_CMP]] to i32
; CHECK-NEXT: br label %exit
; CHECK: exit:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ -1, %entry ], [ [[PHI:%.*]]tmp1, %then ]
; CHECK-NEXT: ret i32 [[PHI]]
;
entry:
%tobool = icmp eq i16 %a, 0
br i1 %tobool, label %then, label %exit
then:
%div = sdiv i16 %c, -1
%cmp = icmp ne i16 %div, 0
br label %exit
exit:
%phi = phi i1 [ false, %entry ], [ %cmp, %then ]
%zext = zext i1 %phi to i32
%add = add nsw i32 %zext, -1
ret i32 %add
}
define i32 @icmp_div2(i16 %a, i16 %c) {
; CHECK-LABEL: @icmp_div2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp eq i16 %a, 0
; CHECK-NEXT: br i1 [[TOBOOL]], label %then, label %exit
; CHECK: then:
; CHECK-NEXT: br label %exit
; CHECK: exit:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ -1, %entry ], [ 0, %then ]
; CHECK-NEXT: ret i32 [[PHI]]
;
entry:
%tobool = icmp eq i16 %a, 0
br i1 %tobool, label %then, label %exit
then:
%div = sdiv i16 %c, 0
%cmp = icmp ne i16 %div, 0
br label %exit
exit:
%phi = phi i1 [ false, %entry ], [ %cmp, %then ]
%zext = zext i1 %phi to i32
%add = add nsw i32 %zext, -1
ret i32 %add
}
define i32 @icmp_div3(i16 %a, i16 %c) {
; CHECK-LABEL: @icmp_div3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp eq i16 %a, 0
; CHECK-NEXT: br i1 [[TOBOOL]], label %then, label %exit
; CHECK: then:
; CHECK-NEXT: [[NOT_CMP:%.*]] = icmp eq i16 %c, 0
; CHECK-NEXT: [[PHITMP1:%.*]] = sext i1 [[NOT_CMP]] to i32
; CHECK-NEXT: br label %exit
; CHECK: exit:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ -1, %entry ], [ [[PHI:%.*]]tmp1, %then ]
; CHECK-NEXT: ret i32 [[PHI]]
;
entry:
%tobool = icmp eq i16 %a, 0
br i1 %tobool, label %then, label %exit
then:
%div = sdiv i16 %c, 1
%cmp = icmp ne i16 %div, 0
br label %exit
exit:
%phi = phi i1 [ false, %entry ], [ %cmp, %then ]
%zext = zext i1 %phi to i32
%add = add nsw i32 %zext, -1
ret i32 %add
}