[clang] [llvm] [X86] Support branch hint (PR #97721)

[Shengchen Kan via cfe-commits]

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KanRobert wrote:

This test is too verbose, not robust and miss coverage.  I would suggest the following
```
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
; RUN: llc < %s -mtriple=x86_64 -mattr=+branch-hint -branch-hint | FileCheck %s
; RUN: llc < %s -mtriple=x86_64 -mattr=+branch-hint -branch-hint -branch-hint-probability-threshold=50 | FileCheck %s
; RUN: llc < %s -mtriple=x86_64 -mattr=+branch-hint -branch-hint -branch-hint-probability-threshold=60 -tail-dup-placement=false | FileCheck --check-prefix=TH60 %s

define void @p51(i32 %x, ptr %p) {
; CHECK-LABEL: p51:
; CHECK:       # %bb.0: # %entry
; CHECK-NEXT:    testl %edi, %edi
; CHECK-NEXT:    ds
; CHECK-NEXT:    je .LBB0_2
; CHECK-NEXT:  # %bb.1: # %if.then
; CHECK-NEXT:    movl %edi, (%rsi)
; CHECK-NEXT:  .LBB0_2: # %if.end
; CHECK-NEXT:    retq
;
; TH60-LABEL: p51:
; TH60:       # %bb.0: # %entry
; TH60-NEXT:    testl %edi, %edi
; TH60-NEXT:    je .LBB0_2
; TH60-NEXT:  # %bb.1: # %if.then
; TH60-NEXT:    movl %edi, (%rsi)
; TH60-NEXT:  .LBB0_2: # %if.end
; TH60-NEXT:    retq
entry:
  %tobool.not = icmp eq i32 %x, 0
  br i1 %tobool.not, label %if.end, label %if.then, !prof !0

if.then:
  store i32 %x, ptr %p, align 4
  br label %if.end

if.end:
  ret void
}

define void @p61(i32 %x, ptr %p) {
; CHECK-LABEL: p61:
; CHECK:       # %bb.0: # %entry
; CHECK-NEXT:    testl %edi, %edi
; CHECK-NEXT:    jne .LBB1_1
; CHECK-NEXT:  # %bb.2: # %if.end
; CHECK-NEXT:    retq
; CHECK-NEXT:  .LBB1_1: # %if.then
; CHECK-NEXT:    movl %edi, (%rsi)
; CHECK-NEXT:    retq
;
; TH60-LABEL: p61:
; TH60:       # %bb.0: # %entry
; TH60-NEXT:    testl %edi, %edi
; TH60-NEXT:    ds
; TH60-NEXT:    je .LBB1_2
; TH60-NEXT:  # %bb.1: # %if.then
; TH60-NEXT:    movl %edi, (%rsi)
; TH60-NEXT:  .LBB1_2: # %if.end
; TH60-NEXT:    retq
entry:
  %tobool.not = icmp eq i32 %x, 0
  br i1 %tobool.not, label %if.end, label %if.then, !prof !1

if.then:
  store i32 %x, ptr %p, align 4
  br label %if.end

if.end:
  ret void
}
```



https://github.com/llvm/llvm-project/pull/97721