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[SimplifyCFG] Fix assertion failure when reusing table switch comparison

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After D116332, some icmps no longer fold with the target-independent
constant folder. The SimplifyCFG code assumed that the comparison
would always fold, which is not guaranteed. Explicitly check that the
result is either true or false.

Differential Revision: https://reviews.llvm.org/D117184
This commit is contained in:
pvellien 2022-01-18 09:27:40 +01:00 committed by Nikita Popov
parent 9c195bae31
commit 4e1c207726
2 changed files with 45 additions and 3 deletions
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5
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -5805,10 +5805,9 @@ static void reuseTableCompare(
for (auto ValuePair : Values) {
Constant *CaseConst = ConstantExpr::getICmp(CmpInst->getPredicate(),
ValuePair.second, CmpOp1, true);
if (!CaseConst || CaseConst == DefaultConst || isa<UndefValue>(CaseConst))
if (!CaseConst || CaseConst == DefaultConst ||
(CaseConst != TrueConst && CaseConst != FalseConst))
return;
assert((CaseConst == TrueConst || CaseConst == FalseConst) &&
"Expect true or false as compare result.");
}
// Check if the branch instruction dominates the phi node. It's a simple

43
llvm/test/Transforms/SimplifyCFG/X86/switch-to-lookup-globals.ll Normal file
View File

@ -0,0 +1,43 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: -p
; RUN: opt -S -passes="simplifycfg<switch-to-lookup>" < %s | FileCheck %s
target triple = "x86_64-unknown-linux-gnu"
%struct.ham = type <{ i32, i32, i32, i8, i8, [2 x i8] }>
@global = external constant [75 x { i32, i32, i32, i8, i8 }]
define i1 @zot(i32 %arg) {
; CHECK-LABEL: @zot(
; CHECK-NEXT: bb:
; CHECK-NEXT: %0 = icmp ult i32 %arg, 3
; CHECK-NEXT: br i1 %0, label %switch.lookup, label %bb6
; CHECK: switch.lookup:
; CHECK-NEXT: %switch.gep = getelementptr inbounds [3 x %struct.ham*], [3 x %struct.ham*]* @switch.table.zot, i32 0, i32 %arg
; CHECK-NEXT: %switch.load = load %struct.ham*, %struct.ham** %switch.gep, align 8
; CHECK-NEXT: br label %bb6
; CHECK: bb6:
; CHECK-NEXT: %tmp7 = phi %struct.ham* [ %switch.load, %switch.lookup ], [ null, %bb ]
; CHECK-NEXT: %tmp8 = icmp eq %struct.ham* %tmp7, bitcast (i32* getelementptr inbounds ([75 x { i32, i32, i32, i8, i8 }], [75 x { i32, i32, i32, i8, i8 }]* @global, i64 1, i64 0, i32 0) to %struct.ham*)
; CHECK-NEXT: ret i1 %tmp8
;
bb:
%tmp = icmp eq i32 %arg, 1
br i1 %tmp, label %bb6, label %bb1
bb1: ; preds = %bb
%tmp2 = icmp eq i32 %arg, 2
br i1 %tmp2, label %bb6, label %bb3
bb3: ; preds = %bb1
%tmp4 = icmp eq i32 %arg, 0
br i1 %tmp4, label %bb6, label %bb5
bb5: ; preds = %bb3
br label %bb6
bb6: ; preds = %bb5, %bb3, %bb1, %bb
%tmp7 = phi %struct.ham* [ null, %bb5 ], [ bitcast (i32* getelementptr inbounds ([75 x { i32, i32, i32, i8, i8 }], [75 x { i32, i32, i32, i8, i8 }]* @global, i64 0, i64 6, i32 0) to %struct.ham*), %bb ], [ null, %bb1 ], [ null, %bb3 ]
%tmp8 = icmp eq %struct.ham* %tmp7, bitcast (i32* getelementptr inbounds ([75 x { i32, i32, i32, i8, i8 }], [75 x { i32, i32, i32, i8, i8 }]* @global, i64 1, i64 0, i32 0) to %struct.ham*)
ret i1 %tmp8
}