371fcb720e
That transformation is lossy, as discussed in https://github.com/llvm/llvm-project/issues/53853 and https://github.com/rust-lang/rust/issues/85133#issuecomment-904185574 This is an alternative to D119839, which would add a limited IPSCCP into SimplifyCFG. Unlike lowering switch to lookup, we still want this transformation to happen relatively early, but after giving a chance for the things like CVP to do their thing. It seems like deferring it just until the IPSCCP is enough for the tests at hand, but perhaps we need to be more aggressive and disable it until CVP. Fixes https://github.com/llvm/llvm-project/issues/53853 Refs. https://github.com/rust-lang/rust/issues/85133 Reviewed By: nikic Differential Revision: https://reviews.llvm.org/D119854
148 lines
3.6 KiB
LLVM
148 lines
3.6 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -switch-range-to-icmp -S | FileCheck %s
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declare i32 @f(i32)
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define i32 @basic(i32 %x) {
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; CHECK-LABEL: @basic(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[X_OFF:%.*]] = add i32 [[X:%.*]], -5
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; CHECK-NEXT: [[SWITCH:%.*]] = icmp ult i32 [[X_OFF]], 3
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; CHECK-NEXT: br i1 [[SWITCH]], label [[A:%.*]], label [[DEFAULT:%.*]]
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; CHECK: common.ret:
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; CHECK-NEXT: [[COMMON_RET_OP:%.*]] = phi i32 [ [[TMP0:%.*]], [[DEFAULT]] ], [ [[TMP1:%.*]], [[A]] ]
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; CHECK-NEXT: ret i32 [[COMMON_RET_OP]]
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; CHECK: default:
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; CHECK-NEXT: [[TMP0]] = call i32 @f(i32 0)
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; CHECK-NEXT: br label [[COMMON_RET:%.*]]
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; CHECK: a:
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; CHECK-NEXT: [[TMP1]] = call i32 @f(i32 1)
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; CHECK-NEXT: br label [[COMMON_RET]]
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;
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entry:
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switch i32 %x, label %default [
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i32 5, label %a
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i32 6, label %a
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i32 7, label %a
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]
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default:
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%0 = call i32 @f(i32 0)
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ret i32 %0
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a:
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%1 = call i32 @f(i32 1)
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ret i32 %1
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}
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define i32 @unreachable(i32 %x) {
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; CHECK-LABEL: @unreachable(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[X_OFF:%.*]] = add i32 [[X:%.*]], -5
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; CHECK-NEXT: [[SWITCH:%.*]] = icmp ult i32 [[X_OFF]], 3
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; CHECK-NEXT: br i1 [[SWITCH]], label [[A:%.*]], label [[B:%.*]]
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; CHECK: common.ret:
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; CHECK-NEXT: [[COMMON_RET_OP:%.*]] = phi i32 [ [[TMP0:%.*]], [[A]] ], [ [[TMP1:%.*]], [[B]] ]
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; CHECK-NEXT: ret i32 [[COMMON_RET_OP]]
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; CHECK: a:
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; CHECK-NEXT: [[TMP0]] = call i32 @f(i32 0)
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; CHECK-NEXT: br label [[COMMON_RET:%.*]]
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; CHECK: b:
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; CHECK-NEXT: [[TMP1]] = call i32 @f(i32 1)
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; CHECK-NEXT: br label [[COMMON_RET]]
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;
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entry:
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switch i32 %x, label %unreachable [
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i32 5, label %a
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i32 6, label %a
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i32 7, label %a
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i32 10, label %b
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i32 20, label %b
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i32 30, label %b
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i32 40, label %b
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]
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unreachable:
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unreachable
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a:
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%0 = call i32 @f(i32 0)
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ret i32 %0
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b:
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%1 = call i32 @f(i32 1)
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ret i32 %1
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}
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define i32 @unreachable2(i32 %x) {
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; CHECK-LABEL: @unreachable2(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[X_OFF:%.*]] = add i32 [[X:%.*]], -5
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; CHECK-NEXT: [[SWITCH:%.*]] = icmp ult i32 [[X_OFF]], 3
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; CHECK-NEXT: br i1 [[SWITCH]], label [[A:%.*]], label [[B:%.*]]
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; CHECK: common.ret:
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; CHECK-NEXT: [[COMMON_RET_OP:%.*]] = phi i32 [ [[TMP0:%.*]], [[A]] ], [ [[TMP1:%.*]], [[B]] ]
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; CHECK-NEXT: ret i32 [[COMMON_RET_OP]]
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; CHECK: a:
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; CHECK-NEXT: [[TMP0]] = call i32 @f(i32 0)
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; CHECK-NEXT: br label [[COMMON_RET:%.*]]
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; CHECK: b:
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; CHECK-NEXT: [[TMP1]] = call i32 @f(i32 1)
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; CHECK-NEXT: br label [[COMMON_RET]]
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;
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entry:
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; Note: folding the most popular case destination into the default
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; would prevent switch-to-icmp here.
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switch i32 %x, label %unreachable [
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i32 5, label %a
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i32 6, label %a
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i32 7, label %a
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i32 10, label %b
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i32 20, label %b
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]
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unreachable:
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unreachable
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a:
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%0 = call i32 @f(i32 0)
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ret i32 %0
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b:
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%1 = call i32 @f(i32 1)
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ret i32 %1
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}
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; This would crash because we did not clean up the
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; default block of the switch before removing the switch.
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define void @PR42737(i32* %a, i1 %c) {
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; CHECK-LABEL: @PR42737(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: unreachable
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;
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entry:
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br i1 %c, label %switch, label %else
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else:
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store i32 2, i32* %a
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br label %switch
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switch:
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%cleanup.dest1 = phi i32 [ 0, %else ], [ 3, %entry ]
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switch i32 %cleanup.dest1, label %unreach1 [
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i32 0, label %cleanup1
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i32 3, label %cleanup2
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]
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cleanup1:
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br label %unreach2
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cleanup2:
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br label %unreach2
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unreach1:
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%phi2 = phi i32 [ %cleanup.dest1, %switch ]
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unreachable
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unreach2:
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unreachable
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}
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