2a721374ae
Following some recent discussions, this changes the representation
of callbrs in IR. The current blockaddress arguments are replaced
with `!` label constraints that refer directly to callbr indirect
destinations:
; Before:
%res = callbr i8* asm "", "=r,r,i"(i8* %x, i8* blockaddress(@test8, %foo))
to label %asm.fallthrough [label %foo]
; After:
%res = callbr i8* asm "", "=r,r,!i"(i8* %x)
to label %asm.fallthrough [label %foo]
The benefit of this is that we can easily update the successors of
a callbr, without having to worry about also updating blockaddress
references. This should allow us to remove some limitations:
* Allow unrolling/peeling/rotation of callbr, or any other
clone-based optimizations
(https://github.com/llvm/llvm-project/issues/41834)
* Allow duplicate successors
(https://github.com/llvm/llvm-project/issues/45248)
This is just the IR representation change though, I will follow up
with patches to remove limtations in various transformation passes
that are no longer needed.
Differential Revision: https://reviews.llvm.org/D129288
59 lines
1.9 KiB
LLVM
59 lines
1.9 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -S -jump-threading | FileCheck %s
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; This test used to cause jump threading to try to split an edge of a callbr.
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@a = global i32 0
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define i32 @c() {
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; CHECK-LABEL: @c(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[TMP0:%.*]] = load i32, i32* @a, align 4
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; CHECK-NEXT: [[TOBOOL:%.*]] = icmp eq i32 [[TMP0]], 0
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; CHECK-NEXT: br i1 [[TOBOOL]], label [[IF_ELSE:%.*]], label [[IF_END:%.*]]
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; CHECK: if.else:
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; CHECK-NEXT: callbr void asm sideeffect "", "!i"()
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; CHECK-NEXT: to label [[NORMAL:%.*]] [label %if.then2]
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; CHECK: normal:
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; CHECK-NEXT: br label [[IF_THEN2:%.*]]
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; CHECK: if.end:
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; CHECK-NEXT: [[CALL:%.*]] = call i32 @b()
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; CHECK-NEXT: [[PHITMP:%.*]] = icmp ne i32 [[CALL]], 0
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; CHECK-NEXT: br i1 [[PHITMP]], label [[IF_THEN2]], label [[IF_END4:%.*]]
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; CHECK: if.then2:
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; CHECK-NEXT: [[CALL3:%.*]] = call i32 @b()
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; CHECK-NEXT: br label [[IF_END4]]
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; CHECK: if.end4:
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; CHECK-NEXT: ret i32 undef
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;
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entry:
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%0 = load i32, i32* @a
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%tobool = icmp eq i32 %0, 0
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br i1 %tobool, label %if.else, label %if.then
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if.then: ; preds = %entry
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%call = call i32 @b() #2
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%phitmp = icmp ne i32 %call, 0
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br label %if.end
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if.else: ; preds = %entry
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callbr void asm sideeffect "", "!i"() #2
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to label %normal [label %if.end]
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normal: ; preds = %if.else
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br label %if.end
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if.end: ; preds = %if.else, %normal, %if.then
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%d.0 = phi i1 [ %phitmp, %if.then ], [ undef, %normal ], [ undef, %if.else ]
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br i1 %d.0, label %if.then2, label %if.end4
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if.then2: ; preds = %if.end
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%call3 = call i32 @b()
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br label %if.end4
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if.end4: ; preds = %if.then2, %if.end
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ret i32 undef
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}
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declare i32 @b()
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