[simplifycfg][NFC] add tests for cross block compare instructions fold and optimization.

[yinyuefengyi]

Summary

e.g. for 3 consecutive nested condition blocks,

B1: if(s >= t) {
     bar1(s, t);
B2:  if( s != t ) {
      bar2(s, t);
B3:    if( s<=t ) {
      bar3(s, t);
    }
  }
}

If s >= t in B1, and s != t in B2, then we can infer s > t, so B3 can be eliminated if B3's condition is s<=t or merged to B2 if it is s > t. Also there other AND ICMP combinations can be folded not listed here.
LLVM IR before opt:

entry:

%cmp = icmp sge i32 %s, %t
br i1 %cmp, label %if.then, label %if.end6

if.then: ; preds = %entry

call void @_Z4bar1ii(i32 signext %s, i32 signext %t)
%cmp1 = icmp ne i32 %s, %t

br i1 %cmp1, label %if.then2, label %if.end6

if.then2: ; preds = %if.then

call void @_Z4bar2ii(i32 signext %s, i32 signext %t)
%cmp3 = icmp sle i32 %s, %t
br i1 %cmp3, label %if.then4, label %if.end6

if.then4: ; preds = %if.then2

call void @_Z4bar3ii(i32 signext %s, i32 signext %t)
br label %if.end6

if.end6: ; preds = %entry, %if.then2, %if.then4, %if.then

ret void

the target code should be:

entry:

%cmp = icmp sge i32 %s, %t
br i1 %cmp, label %if.then, label %if.end6

if.then: ; preds = %entry

call void @_Z4bar1ii(i32 signext %s, i32 signext %t)
%cmp1 = icmp ne i32 %s, %t
br i1 %cmp1, label %if.then2, label %if.end6

if.then2: ; preds = %if.then

call void @_Z4bar2ii(i32 signext %s, i32 signext %t)
br label %if.end6

if.end6: ; preds = %if.then2, %if.then, %entry

ret void

[spatel]

llvm/test/Transforms/SimplifyCFG/branch-fold-three.ll

2 ↗

(On Diff #175631)

This should only be testing with a single -simplifycfg.
If there's a cross-pass dependency that you want to confirm is resolved, then you probably want to add a test to
test/Transforms/PhaseOrdering, but ideally, we will show the key transform using just a single pass.

4 ↗

(On Diff #175631)

You can remove the empty #0/#1 attribute specifiers.

[yinyuefengyi]

use simplifycfg only to avoid pass dependency; remove symbol '#0' and '#1'.

[spatel]

LGTM

llvm/trunk/test/Transforms/SimplifyCFG/branch-fold-three.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -simplifycfg -S | FileCheck %s
+
+; s >= t, s != t, s <= t
+define void @foo1(i32 %s, i32 %t) {
+; CHECK-LABEL: @foo1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i32 [[S:%.*]], [[T:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_END6:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    call void @bar1(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ne i32 [[S]], [[T]]
+; CHECK-NEXT:    br i1 [[CMP1]], label [[IF_THEN2:%.*]], label [[IF_END6]]
+; CHECK:       if.then2:
+; CHECK-NEXT:    call void @bar2(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP3:%.*]] = icmp sle i32 [[S]], [[T]]
+; CHECK-NEXT:    br i1 [[CMP3]], label [[IF_THEN4:%.*]], label [[IF_END6]]
+; CHECK:       if.then4:
+; CHECK-NEXT:    call void @bar3(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    br label [[IF_END6]]
+; CHECK:       if.end6:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp = icmp sge i32 %s, %t
+  br i1 %cmp, label %if.then, label %if.end6
+
+if.then:
+  call void @bar1(i32 %s, i32 %t)
+  %cmp1 = icmp ne i32 %s, %t
+  br i1 %cmp1, label %if.then2, label %if.end6
+
+if.then2:
+  call void @bar2(i32 %s, i32 %t)
+  %cmp3 = icmp sle i32 %s, %t
+  br i1 %cmp3, label %if.then4, label %if.end6
+
+if.then4:
+  call void @bar3(i32 %s, i32 %t)
+  br label %if.end6
+
+if.end6:
+  ret void
+}
+
+; s != t, s >= t, s <= t
+define void @foo11(i32 %s, i32 %t) {
+; CHECK-LABEL: @foo11(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[S:%.*]], [[T:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_END6:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    call void @bar1(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp sge i32 [[S]], [[T]]
+; CHECK-NEXT:    br i1 [[CMP1]], label [[IF_THEN2:%.*]], label [[IF_END6]]
+; CHECK:       if.then2:
+; CHECK-NEXT:    call void @bar2(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP3:%.*]] = icmp sle i32 [[S]], [[T]]
+; CHECK-NEXT:    br i1 [[CMP3]], label [[IF_THEN4:%.*]], label [[IF_END6]]
+; CHECK:       if.then4:
+; CHECK-NEXT:    call void @bar3(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    br label [[IF_END6]]
+; CHECK:       if.end6:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp = icmp ne i32 %s, %t
+  br i1 %cmp, label %if.then, label %if.end6
+
+if.then:
+  call void @bar1(i32 %s, i32 %t)
+  %cmp1 = icmp sge i32 %s, %t
+  br i1 %cmp1, label %if.then2, label %if.end6
+
+if.then2:
+  call void @bar2(i32 %s, i32 %t)
+  %cmp3 = icmp sle i32 %s, %t
+  br i1 %cmp3, label %if.then4, label %if.end6
+
+if.then4:
+  call void @bar3(i32 %s, i32 %t)
+  br label %if.end6
+
+if.end6:
+  ret void
+}
+
+; s >= t, t != s, s <= t
+define void @foo2(i32 %s, i32 %t) {
+; CHECK-LABEL: @foo2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i32 [[S:%.*]], [[T:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_END6:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    call void @bar1(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ne i32 [[T]], [[S]]
+; CHECK-NEXT:    br i1 [[CMP1]], label [[IF_THEN2:%.*]], label [[IF_END6]]
+; CHECK:       if.then2:
+; CHECK-NEXT:    call void @bar2(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP3:%.*]] = icmp sle i32 [[S]], [[T]]
+; CHECK-NEXT:    br i1 [[CMP3]], label [[IF_THEN4:%.*]], label [[IF_END6]]
+; CHECK:       if.then4:
+; CHECK-NEXT:    call void @bar3(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    br label [[IF_END6]]
+; CHECK:       if.end6:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp = icmp sge i32 %s, %t
+  br i1 %cmp, label %if.then, label %if.end6
+
+if.then:
+  call void @bar1(i32 %s, i32 %t)
+  %cmp1 = icmp ne i32 %t, %s
+  br i1 %cmp1, label %if.then2, label %if.end6
+
+if.then2:
+  call void @bar2(i32 %s, i32 %t)
+  %cmp3 = icmp sle i32 %s, %t
+  br i1 %cmp3, label %if.then4, label %if.end6
+
+if.then4:
+  call void @bar3(i32 %s, i32 %t)
+  br label %if.end6
+
+if.end6:
+  ret void
+}
+
+; s != t, t <= s, s <= t
+define void @foo21(i32 %s, i32 %t) {
+; CHECK-LABEL: @foo21(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[S:%.*]], [[T:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_END6:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    call void @bar1(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp sle i32 [[T]], [[S]]
+; CHECK-NEXT:    br i1 [[CMP1]], label [[IF_THEN2:%.*]], label [[IF_END6]]
+; CHECK:       if.then2:
+; CHECK-NEXT:    call void @bar2(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP3:%.*]] = icmp sle i32 [[S]], [[T]]
+; CHECK-NEXT:    br i1 [[CMP3]], label [[IF_THEN4:%.*]], label [[IF_END6]]
+; CHECK:       if.then4:
+; CHECK-NEXT:    call void @bar3(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    br label [[IF_END6]]
+; CHECK:       if.end6:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp = icmp ne i32 %s, %t
+  br i1 %cmp, label %if.then, label %if.end6
+
+if.then:
+  call void @bar1(i32 %s, i32 %t)
+  %cmp1 = icmp sle i32 %t, %s
+  br i1 %cmp1, label %if.then2, label %if.end6
+
+if.then2:
+  call void @bar2(i32 %s, i32 %t)
+  %cmp3 = icmp sle i32 %s, %t
+  br i1 %cmp3, label %if.then4, label %if.end6
+
+if.then4:
+  call void @bar3(i32 %s, i32 %t)
+  br label %if.end6
+
+if.end6:
+  ret void
+}
+
+; t <= s, t != s, s <= t
+define void @foo3(i32 %s, i32 %t) {
+; CHECK-LABEL: @foo3(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i32 [[T:%.*]], [[S:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_END6:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    call void @bar1(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ne i32 [[T]], [[S]]
+; CHECK-NEXT:    br i1 [[CMP1]], label [[IF_THEN2:%.*]], label [[IF_END6]]
+; CHECK:       if.then2:
+; CHECK-NEXT:    call void @bar2(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP3:%.*]] = icmp sle i32 [[S]], [[T]]
+; CHECK-NEXT:    br i1 [[CMP3]], label [[IF_THEN4:%.*]], label [[IF_END6]]
+; CHECK:       if.then4:
+; CHECK-NEXT:    call void @bar3(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    br label [[IF_END6]]
+; CHECK:       if.end6:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp = icmp sle i32 %t, %s
+  br i1 %cmp, label %if.then, label %if.end6
+
+if.then:
+  call void @bar1(i32 %s, i32 %t)
+  %cmp1 = icmp ne i32 %t, %s
+  br i1 %cmp1, label %if.then2, label %if.end6
+
+if.then2:
+  call void @bar2(i32 %s, i32 %t)
+  %cmp3 = icmp sle i32 %s, %t
+  br i1 %cmp3, label %if.then4, label %if.end6
+
+if.then4:
+  call void @bar3(i32 %s, i32 %t)
+  br label %if.end6
+
+if.end6:
+  ret void
+}
+
+; t != s, t <= s, s <= t
+define void @foo31(i32 %s, i32 %t) {
+; CHECK-LABEL: @foo31(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[T:%.*]], [[S:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_END6:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    call void @bar1(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp sle i32 [[T]], [[S]]
+; CHECK-NEXT:    br i1 [[CMP1]], label [[IF_THEN2:%.*]], label [[IF_END6]]
+; CHECK:       if.then2:
+; CHECK-NEXT:    call void @bar2(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    [[CMP3:%.*]] = icmp sle i32 [[S]], [[T]]
+; CHECK-NEXT:    br i1 [[CMP3]], label [[IF_THEN4:%.*]], label [[IF_END6]]
+; CHECK:       if.then4:
+; CHECK-NEXT:    call void @bar3(i32 [[S]], i32 [[T]])
+; CHECK-NEXT:    br label [[IF_END6]]
+; CHECK:       if.end6:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp = icmp ne i32 %t, %s
+  br i1 %cmp, label %if.then, label %if.end6
+
+if.then:
+  call void @bar1(i32 %s, i32 %t)
+  %cmp1 = icmp sle i32 %t, %s
+  br i1 %cmp1, label %if.then2, label %if.end6
+
+if.then2:
+  call void @bar2(i32 %s, i32 %t)
+  %cmp3 = icmp sle i32 %s, %t
+  br i1 %cmp3, label %if.then4, label %if.end6
+
+if.then4:
+  call void @bar3(i32 %s, i32 %t)
+  br label %if.end6
+
+if.end6:
+  ret void
+}
+
+declare void @bar1(i32, i32)
+declare void @bar2(i32, i32)
+declare void @bar3(i32, i32)
+