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[Attributor][FIX] Collapse `undef` to a proper value 

If we see an undef we cannot assume it's the same as "no value". For now
we just collapse it to 0.
This commit is contained in:
Johannes Doerfert 2020-02-14 20:08:20 -06:00
parent 137c99a6a5
commit b53af0e7f9
3 changed files with 63 additions and 3 deletions
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2
llvm/lib/Transforms/IPO/Attributor.cpp
View File

@ -6656,6 +6656,8 @@ struct AAValueConstantRangeFloating : AAValueConstantRangeImpl {
}
if (isa<UndefValue>(&V)) {
// Collapse the undef state to 0.
unionAssumed(ConstantRange(APInt(getBitWidth(), 0)));
indicateOptimisticFixpoint();
return;
}

59
llvm/test/Transforms/Attributor/range.ll
View File

@ -1214,6 +1214,65 @@ define i1 @fcmp_caller(float %fa, float %fb, double %da, double %db, double* %dp
ret i1 %o3
}
define i8 @ret_two() {
; CHECK-LABEL: define {{[^@]+}}@ret_two()
; CHECK-NEXT: ret i8 2
;
ret i8 2
}
define i8 @ret_undef() {
; CHECK-LABEL: define {{[^@]+}}@ret_undef()
; CHECK-NEXT: ret i8 undef
;
ret i8 undef
}
; Verify we collapse undef to a value and return something non-undef here.
define i8 @undef_collapse_1() {
; CHECK-LABEL: define {{[^@]+}}@undef_collapse_1()
; CHECK-NEXT: ret i8 0
;
%c = call i8 @ret_undef()
%s = shl i8 %c, 2
ret i8 %s
}
; Verify we collapse undef to a value and return something non-undef here.
define i8 @undef_collapse_2() {
; CHECK-LABEL: define {{[^@]+}}@undef_collapse_2()
; CHECK-NEXT: ret i8 0
;
%c = call i8 @ret_two()
%s = shl i8 undef, %c
ret i8 %s
}
define i8 @undef_collapse_caller() {
; OLD_PM-LABEL: define {{[^@]+}}@undef_collapse_caller()
; OLD_PM-NEXT: ret i8 0
;
; NEW_PM-LABEL: define {{[^@]+}}@undef_collapse_caller()
; NEW_PM-NEXT: ret i8 0
;
; CGSCC_OLD_PM-LABEL: define {{[^@]+}}@undef_collapse_caller()
; CGSCC_OLD_PM-NEXT: [[C1:%.*]] = call i8 @undef_collapse_1()
; CGSCC_OLD_PM-NEXT: [[C2:%.*]] = call i8 @undef_collapse_2()
; CGSCC_OLD_PM-NEXT: [[A:%.*]] = add i8 [[C1]], [[C2]]
; CGSCC_OLD_PM-NEXT: ret i8 [[A]]
;
; CGSCC_NEW_PM-LABEL: define {{[^@]+}}@undef_collapse_caller()
; CGSCC_NEW_PM-NEXT: [[C1:%.*]] = call i8 @undef_collapse_1()
; CGSCC_NEW_PM-NEXT: [[C2:%.*]] = call i8 @undef_collapse_2()
; CGSCC_NEW_PM-NEXT: [[A:%.*]] = add i8 [[C1]], [[C2]]
; CGSCC_NEW_PM-NEXT: ret i8 [[A]]
;
%c1 = call i8 @undef_collapse_1()
%c2 = call i8 @undef_collapse_2()
%a = add i8 %c1, %c2
ret i8 %a
}
!0 = !{i32 0, i32 10}
!1 = !{i32 10, i32 100}
; CHECK: !0 = !{i32 0, i32 10}

5
llvm/test/Transforms/Attributor/undefined_behavior.ll
View File

@ -264,10 +264,9 @@ e:
; undef of a previous instruction.
define i32 @cond_br_on_undef3() {
; ATTRIBUTOR-LABEL: @cond_br_on_undef3(
; ATTRIBUTOR-NEXT: %cond = icmp ne i32 1, undef
; ATTRIBUTOR-NEXT: br i1 %cond, label %t, label %e
; ATTRIBUTOR-NEXT: br label %t
; ATTRIBUTOR: t:
; ATTRIBUTOR-NEXT: unreachable
; ATTRIBUTOR-NEXT: ret i32 1
; ATTRIBUTOR: e:
; ATTRIBUTOR-NEXT: unreachable