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9e6192bcdf
Have funcattrs expand all implied attributes into the IR. This expands the infrastructure from D100400, but for definitions not declarations this time. Somewhat subtly, this mostly isn't semantic. Because the accessors did the inference, any client which used the accessor was already getting the stronger result. Clients that directly checked presence of attributes (there are some), will see a stronger result now. The old behavior can end up quite confusing for two reasons: * Without this change, we have situations where function-attrs appears to fail when inferring an attribute (as seen by a human reading IR), but that consuming code will see that it should have been implied. As a human trying to sanity check test results and study IR for optimization possibilities, this is exceeding error prone and confusing. (I'll note that I wasted several hours recently because of this.) * We can have transforms which trigger without the IR appearing (on inspection) to meet the preconditions. This change doesn't prevent this from happening (as the accessors still involve multiple checks), but it should make it less frequent. I'd argue in favor of deleting the extra checks out of the accessors after this lands, but I want that in it's own review as a) it's purely stylistic, and b) I already know there's some disagreement. Once this lands, I'm also going to do a cleanup change which will delete some now redundant duplicate predicates in the inference code, but again, that deserves to be a change of it's own. Differential Revision: https://reviews.llvm.org/D100226
135 lines
5.8 KiB
LLVM
135 lines
5.8 KiB
LLVM
; The CGSCC pass manager includes an SCC iteration utility that tracks indirect
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; calls that are turned into direct calls (devirtualization) and re-visits the
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; SCC to expose those calls to the SCC-based IPO passes. We trigger
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; devirtualization here with GVN which forwards a store through a load and to
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; an indirect call.
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;
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; RUN: opt -aa-pipeline=basic-aa -passes='module(inferattrs),cgscc(function-attrs,function(gvn,instcombine))' -S < %s | FileCheck %s --check-prefix=CHECK --check-prefix=BEFORE
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; RUN: opt -aa-pipeline=basic-aa -passes='module(inferattrs),cgscc(devirt<1>(function-attrs,function(gvn,instcombine)))' -S < %s | FileCheck %s --check-prefix=CHECK --check-prefix=AFTER --check-prefix=AFTER1
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; RUN: opt -aa-pipeline=basic-aa -passes='module(inferattrs),cgscc(devirt<2>(function-attrs,function(gvn,instcombine)))' -S < %s | FileCheck %s --check-prefix=CHECK --check-prefix=AFTER --check-prefix=AFTER2
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;
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; RUN: not --crash opt -abort-on-max-devirt-iterations-reached -aa-pipeline=basic-aa -passes='module(inferattrs),cgscc(devirt<1>(function-attrs,function(gvn,instcombine)))' -S < %s
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; RUN: opt -abort-on-max-devirt-iterations-reached -aa-pipeline=basic-aa -passes='module(inferattrs),cgscc(devirt<2>(function-attrs,function(gvn,instcombine)))' -S < %s
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;
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; We also verify that the real O2 pipeline catches these cases.
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; RUN: opt -aa-pipeline=basic-aa -passes='default<O2>' -S < %s | FileCheck %s --check-prefix=CHECK --check-prefix=AFTER --check-prefix=AFTER2
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declare void @readnone() readnone
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; CHECK: Function Attrs: nofree nosync readnone
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; CHECK-NEXT: declare void @readnone()
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declare void @unknown()
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; CHECK-NOT: Function Attrs
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; CHECK-LABEL: declare void @unknown(){{ *$}}
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; The @test1 function checks that when we refine an indirect call to a direct
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; call we revisit the SCC passes to reflect the more precise information. This
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; is the basic functionality.
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define void @test1() {
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; BEFORE-NOT: Function Attrs
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; AFTER: Function Attrs: nofree nosync readnone
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; CHECK-LABEL: define void @test1()
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entry:
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%fptr = alloca void ()*
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store void ()* @readnone, void ()** %fptr
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%f = load void ()*, void ()** %fptr
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call void %f()
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ret void
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}
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; The @test2_* functions check that when we need multiple (in this case 2)
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; repetitions to compute some state that is incrementally exposed with each
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; one, the limit on repetitions is enforced. So we make progress with
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; one repetition but not as much as with three.
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;
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; This is somewhat awkward to test because we have to contrive to have a state
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; repetition triggered and observed with very few passes. The technique here
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; is to have one indirect call that can only be resolved when the entire SCC is
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; deduced as readonly, and mark that indirect call at the call site as readonly
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; to make that possible. This forces us to first deduce readonly, then
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; devirtualize again, and then deduce readnone.
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declare void @readnone_with_arg(void ()**) readnone
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; CHECK: Function Attrs: nofree nosync readnone
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; CHECK-LABEL: declare void @readnone_with_arg(void ()**)
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define void @test2_a(void ()** %ignore) {
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; BEFORE-NOT: Function Attrs
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; AFTER1: Function Attrs: nofree readonly
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; AFTER2: Function Attrs: nofree nosync readnone
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; BEFORE: define void @test2_a(void ()** %ignore)
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; AFTER: define void @test2_a(void ()** readnone %ignore)
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entry:
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%f1ptr = alloca void (void ()**)*
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store void (void ()**)* @readnone_with_arg, void (void ()**)** %f1ptr
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%f1 = load void (void ()**)*, void (void ()**)** %f1ptr
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; This indirect call is the first to be resolved, allowing us to deduce
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; readonly but not (yet) readnone.
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call void %f1(void ()** %ignore)
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; CHECK: call void @readnone_with_arg(void ()** %ignore)
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; Bogus call to test2_b to make this a cycle.
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call void @test2_b()
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ret void
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}
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define void @test2_b() {
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; BEFORE-NOT: Function Attrs
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; AFTER1: Function Attrs: nofree readonly
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; AFTER2: Function Attrs: nofree nosync readnone
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; CHECK-LABEL: define void @test2_b()
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entry:
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%f2ptr = alloca void ()*
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store void ()* @readnone, void ()** %f2ptr
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; Call the other function here to prevent forwarding until the SCC has had
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; function attrs deduced.
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call void @test2_a(void ()** %f2ptr)
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%f2 = load void ()*, void ()** %f2ptr
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; This is the second indirect call to be resolved, and can only be resolved
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; after we deduce 'readonly' for the rest of the SCC. Once it is
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; devirtualized, we can deduce readnone for the SCC.
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call void %f2() readonly
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; BEFORE: call void %f2()
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; AFTER: call void @readnone()
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ret void
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}
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declare i8* @memcpy(i8*, i8*, i64)
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; CHECK-LABEL: i8* @memcpy(
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; The @test3 function checks that when we refine an indirect call to an
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; intrinsic we still revisit the SCC pass. This also covers cases where the
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; value handle itself doesn't persist due to the nature of how instcombine
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; creates the memcpy intrinsic call, and we rely on the count of indirect calls
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; decreasing and the count of direct calls increasing.
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; Adding 'noinline' attribute to force attributes for improved matching.
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define void @test3(i8* %src, i8* %dest, i64 %size) noinline {
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; CHECK: Function Attrs
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; CHECK-NOT: read
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; CHECK-SAME: noinline
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; BEFORE-LABEL: define void @test3(i8* %src, i8* %dest, i64 %size)
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; AFTER-LABEL: define void @test3(i8* nocapture readonly %src, i8* nocapture %dest, i64 %size)
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%fptr = alloca i8* (i8*, i8*, i64)*
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store i8* (i8*, i8*, i64)* @memcpy, i8* (i8*, i8*, i64)** %fptr
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%f = load i8* (i8*, i8*, i64)*, i8* (i8*, i8*, i64)** %fptr
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call i8* %f(i8* %dest, i8* %src, i64 %size)
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; CHECK: call void @llvm.memcpy
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ret void
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}
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; A boring function that just keeps our declarations around.
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define void @keep(i8** %sink) {
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; CHECK-NOT: Function Attrs
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; CHECK-LABEL: define void @keep(
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entry:
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store volatile i8* bitcast (void ()* @readnone to i8*), i8** %sink
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store volatile i8* bitcast (void ()* @unknown to i8*), i8** %sink
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store volatile i8* bitcast (i8* (i8*, i8*, i64)* @memcpy to i8*), i8** %sink
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call void @unknown()
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ret void
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}
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