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3d150e22ef
Previously, a non-extractvalue use of an aggregate return value meant
the entire return was considered live (the algorithm gave up
entirely). This was correct, but conservative. It's better to actually
look at that Use, making the analysis results apply to all sub-values
under consideration.
E.g.
%val = call { i32, i32 } @whatever()
[...]
ret { i32, i32 } %val
The return is using the entire aggregate (sub-values 0 and 1). We can
still simplify @whatever if we can prove that this return is itself
unused.
Also unifies the logic slightly between aggregate and non-aggregate
cases..
llvm-svn: 228558
71 lines
2.1 KiB
LLVM
71 lines
2.1 KiB
LLVM
; RUN: opt -S -deadargelim %s | FileCheck %s
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; Case 0: the basic example: an entire aggregate use is returned, but it's
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; actually only used in ways we can eliminate. We gain benefit from analysing
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; the "use" and applying its results to all sub-values.
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; CHECK-LABEL: define internal void @agguse_dead()
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define internal { i32, i32 } @agguse_dead() {
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ret { i32, i32 } { i32 0, i32 1 }
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}
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define internal { i32, i32 } @test_agguse_dead() {
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%val = call { i32, i32 } @agguse_dead()
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ret { i32, i32 } %val
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}
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; Case 1: an opaque use of the aggregate exists (in this case dead). Otherwise
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; only one value is used, so function can be simplified.
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; CHECK-LABEL: define internal i32 @rets_independent_if_agguse_dead()
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; CHECK: [[RET:%.*]] = extractvalue { i32, i32 } { i32 0, i32 1 }, 1
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; CHECK: ret i32 [[RET]]
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define internal { i32, i32 } @rets_independent_if_agguse_dead() {
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ret { i32, i32 } { i32 0, i32 1 }
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}
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define internal { i32, i32 } @test_rets_independent_if_agguse_dead(i1 %tst) {
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%val = call { i32, i32 } @rets_independent_if_agguse_dead()
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br i1 %tst, label %use_1, label %use_aggregate
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use_1:
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; This use can be classified as applying only to ret 1.
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%val0 = extractvalue { i32, i32 } %val, 1
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call void @callee(i32 %val0)
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ret { i32, i32 } undef
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use_aggregate:
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; This use is assumed to apply to both 0 and 1.
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ret { i32, i32 } %val
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}
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; Case 2: an opaque use of the aggregate exists (in this case *live*). Other
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; uses shouldn't matter.
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; CHECK-LABEL: define internal { i32, i32 } @rets_live_agguse()
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; CHECK: ret { i32, i32 } { i32 0, i32 1 }
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define internal { i32, i32 } @rets_live_agguse() {
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ret { i32, i32} { i32 0, i32 1 }
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}
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define { i32, i32 } @test_rets_live_aggues(i1 %tst) {
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%val = call { i32, i32 } @rets_live_agguse()
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br i1 %tst, label %use_1, label %use_aggregate
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use_1:
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; This use can be classified as applying only to ret 1.
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%val0 = extractvalue { i32, i32 } %val, 1
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call void @callee(i32 %val0)
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ret { i32, i32 } undef
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use_aggregate:
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; This use is assumed to apply to both 0 and 1.
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ret { i32, i32 } %val
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}
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declare void @callee(i32) |