llvm/test/Transforms/GVN/fake-use-constprop.ll

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
; RUN: opt -passes=gvn -S < %s | FileCheck %s
;
; The Global Value Numbering pass (GVN) propagates boolean values
; that are constant in dominated basic blocks to all the uses
; in these basic blocks. However, we don't want the constant propagated
; into fake.use intrinsics since this would render the intrinsic useless
; with respect to keeping the variable live up until the fake.use.
; This test checks that we don't generate any fake.uses with constant 0.
;
; Reduced from the following test case, generated with clang -O2 -S -emit-llvm -fextend-variable-liveness test.c
;
; extern void func1();
; extern int bar();
; extern void baz(int);
;
; int foo(int i, float f, int *punused)
; {
;   int j = 3*i;
;   if (j > 0) {
;     int m = bar(i);
;     if (m) {
;       char b = f;
;       baz(b);
;       if (b)
;         goto lab;
;       func1();
;     }
; lab:
;     func1();
;   }
;   return 1;
; }

;; GVN should propagate a constant value through to a regular call, but not to
;; a fake use, which should continue to track the original value.

define i32 @foo(float %f) optdebug {
; CHECK-LABEL: define i32 @foo(
; CHECK-SAME: float [[F:%.*]]) #[[ATTR0:[0-9]+]] {
; CHECK-NEXT:    [[CONV:%.*]] = fptosi float [[F]] to i8
; CHECK-NEXT:    [[TOBOOL3:%.*]] = icmp eq i8 [[CONV]], 0
; CHECK-NEXT:    br i1 [[TOBOOL3]], label %[[IF_END:.*]], label %[[LAB:.*]]
; CHECK:       [[IF_END]]:
; CHECK-NEXT:    tail call void (...) @bees(i8 0)
; CHECK-NEXT:    tail call void (...) @llvm.fake.use(i8 [[CONV]])
; CHECK-NEXT:    br label %[[LAB]]
; CHECK:       [[LAB]]:
; CHECK-NEXT:    ret i32 1
;
  %conv = fptosi float %f to i8
  %tobool3 = icmp eq i8 %conv, 0
  br i1 %tobool3, label %if.end, label %lab

if.end:
  tail call void (...) @bees(i8 %conv)
  tail call void (...) @llvm.fake.use(i8 %conv)
  br label %lab

lab:
  ret i32 1
}

declare i32 @bar(...)

declare void @baz(i32)

declare void @bees(i32)

declare void @func1(...)