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[EarlyCSE] Simplify guard intrinsics
Summary: This change teaches EarlyCSE some basic properties of guard intrinsics: - Guard intrinsics read all memory, but don't write to any memory - After a guard has executed, the condition it was guarding on can be assumed to be true - Guard intrinsics on a constant `true` are no-ops Reviewers: reames, hfinkel Subscribers: mcrosier, llvm-commits Differential Revision: http://reviews.llvm.org/D19578 llvm-svn: 268120
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; RUN: opt -S -early-cse < %s | FileCheck %s | ||
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declare void @llvm.experimental.guard(i1,...) | ||
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define i32 @test0(i32* %ptr, i1 %cond) { | ||
; We can do store to load forwarding over a guard, since it does not | ||
; clobber memory | ||
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; CHECK-LABEL: @test0( | ||
; CHECK-NEXT: store i32 40, i32* %ptr | ||
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ] | ||
; CHECK-NEXT: ret i32 40 | ||
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store i32 40, i32* %ptr | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ] | ||
%rval = load i32, i32* %ptr | ||
ret i32 %rval | ||
} | ||
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define i32 @test1(i32* %val, i1 %cond) { | ||
; We can CSE loads over a guard, since it does not clobber memory | ||
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; CHECK-LABEL: @test1( | ||
; CHECK-NEXT: %val0 = load i32, i32* %val | ||
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ] | ||
; CHECK-NEXT: ret i32 0 | ||
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%val0 = load i32, i32* %val | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ] | ||
%val1 = load i32, i32* %val | ||
%rval = sub i32 %val0, %val1 | ||
ret i32 %rval | ||
} | ||
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define i32 @test2() { | ||
; Guards on "true" get removed | ||
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; CHECK-LABEL: @test2( | ||
; CHECK-NEXT: ret i32 0 | ||
call void(i1, ...) @llvm.experimental.guard(i1 true) [ "deopt"() ] | ||
ret i32 0 | ||
} | ||
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define i32 @test3(i32 %val) { | ||
; After a guard has executed the condition it was guarding is known to | ||
; be true. | ||
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; CHECK-LABEL: @test3( | ||
; CHECK-NEXT: %cond0 = icmp slt i32 %val, 40 | ||
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ] | ||
; CHECK-NEXT: ret i32 -1 | ||
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%cond0 = icmp slt i32 %val, 40 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ] | ||
%cond1 = icmp slt i32 %val, 40 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ] | ||
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%cond2 = icmp slt i32 %val, 40 | ||
%rval = sext i1 %cond2 to i32 | ||
ret i32 %rval | ||
} | ||
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define i32 @test3.unhandled(i32 %val) { | ||
; After a guard has executed the condition it was guarding is known to | ||
; be true. | ||
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; CHECK-LABEL: @test3.unhandled( | ||
; CHECK-NEXT: %cond0 = icmp slt i32 %val, 40 | ||
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ] | ||
; CHECK-NEXT: %cond1 = icmp sge i32 %val, 40 | ||
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ] | ||
; CHECK-NEXT: ret i32 0 | ||
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; Demonstrates a case we do not yet handle (it is legal to fold %cond2 | ||
; to false) | ||
%cond0 = icmp slt i32 %val, 40 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ] | ||
%cond1 = icmp sge i32 %val, 40 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ] | ||
ret i32 0 | ||
} | ||
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define i32 @test4(i32 %val, i1 %c) { | ||
; Same as test3, but with some control flow involved. | ||
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; CHECK-LABEL: @test4( | ||
; CHECK: entry: | ||
; CHECK-NEXT: %cond0 = icmp slt i32 %val, 40 | ||
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond0 | ||
; CHECK-NEXT: br label %bb0 | ||
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; CHECK: bb0: | ||
; CHECK-NEXT: %cond2 = icmp ult i32 %val, 200 | ||
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond2 | ||
; CHECK-NEXT: br i1 %c, label %left, label %right | ||
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; CHECK: left: | ||
; CHECK-NEXT: ret i32 0 | ||
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; CHECK: right: | ||
; CHECK-NEXT: ret i32 20 | ||
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entry: | ||
%cond0 = icmp slt i32 %val, 40 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ] | ||
%cond1 = icmp slt i32 %val, 40 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ] | ||
br label %bb0 | ||
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bb0: | ||
%cond2 = icmp ult i32 %val, 200 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond2) [ "deopt"() ] | ||
br i1 %c, label %left, label %right | ||
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left: | ||
%cond3 = icmp ult i32 %val, 200 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond3) [ "deopt"() ] | ||
ret i32 0 | ||
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right: | ||
ret i32 20 | ||
} | ||
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define i32 @test5(i32 %val, i1 %c) { | ||
; Same as test4, but the %left block has mutliple predecessors. | ||
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; CHECK-LABEL: @test5( | ||
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; CHECK: entry: | ||
; CHECK-NEXT: %cond0 = icmp slt i32 %val, 40 | ||
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond0 | ||
; CHECK-NEXT: br label %bb0 | ||
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; CHECK: bb0: | ||
; CHECK-NEXT: %cond2 = icmp ult i32 %val, 200 | ||
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond2 | ||
; CHECK-NEXT: br i1 %c, label %left, label %right | ||
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; CHECK: left: | ||
; CHECK-NEXT: br label %right | ||
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; CHECK: right: | ||
; CHECK-NEXT: br label %left | ||
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entry: | ||
%cond0 = icmp slt i32 %val, 40 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ] | ||
%cond1 = icmp slt i32 %val, 40 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ] | ||
br label %bb0 | ||
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bb0: | ||
%cond2 = icmp ult i32 %val, 200 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond2) [ "deopt"() ] | ||
br i1 %c, label %left, label %right | ||
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left: | ||
%cond3 = icmp ult i32 %val, 200 | ||
call void(i1,...) @llvm.experimental.guard(i1 %cond3) [ "deopt"() ] | ||
br label %right | ||
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right: | ||
br label %left | ||
} | ||
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define void @test6(i1 %c, i32* %ptr) { | ||
; Check that we do not DSE over calls to @llvm.experimental.guard. | ||
; Guard intrinsics do _read_ memory, so th call to guard below needs | ||
; to see the store of 500 to %ptr | ||
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; CHECK-LABEL: @test6( | ||
; CHECK-NEXT: store i32 500, i32* %ptr | ||
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %c) [ "deopt"() ] | ||
; CHECK-NEXT: store i32 600, i32* %ptr | ||
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store i32 500, i32* %ptr | ||
call void(i1,...) @llvm.experimental.guard(i1 %c) [ "deopt"() ] | ||
store i32 600, i32* %ptr | ||
ret void | ||
} |