[llvm] [CVP] Infer nneg on existing zext (PR #72052)

[Yingwei Zheng via llvm-commits]

================
@@ -0,0 +1,179 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=correlated-propagation -S | FileCheck %s
+
+; Check that debug locations are preserved. For more info see:
+;   https://llvm.org/docs/SourceLevelDebugging.html#fixing-errors
+; RUN: opt < %s -enable-debugify -passes=correlated-propagation -S 2>&1 | \
+; RUN:   FileCheck %s -check-prefix=DEBUG
+; DEBUG: CheckModuleDebugify: PASS
+
+declare void @use64(i64)
+
+define void @test1(i32 %n) {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[FOR_COND:%.*]]
+; CHECK:       for.cond:
+; CHECK-NEXT:    [[A:%.*]] = phi i32 [ [[N:%.*]], [[ENTRY:%.*]] ], [ [[EXT:%.*]], [[FOR_BODY:%.*]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[A]], -1
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[EXT_WIDE:%.*]] = zext nneg i32 [[A]] to i64
+; CHECK-NEXT:    call void @use64(i64 [[EXT_WIDE]])
+; CHECK-NEXT:    [[EXT]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT:    br label [[FOR_COND]]
+; CHECK:       for.end:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %a = phi i32 [ %n, %entry ], [ %ext, %for.body ]
+  %cmp = icmp sgt i32 %a, -1
+  br i1 %cmp, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond
+  %ext.wide = zext i32 %a to i64
+  call void @use64(i64 %ext.wide)
+  %ext = trunc i64 %ext.wide to i32
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  ret void
+}
+
+;; Negative test to show transform doesn't happen unless n >= 0.
+define void @test2(i32 %n) {
+; CHECK-LABEL: @test2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[FOR_COND:%.*]]
+; CHECK:       for.cond:
+; CHECK-NEXT:    [[A:%.*]] = phi i32 [ [[N:%.*]], [[ENTRY:%.*]] ], [ [[EXT:%.*]], [[FOR_BODY:%.*]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[A]], -2
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[EXT_WIDE:%.*]] = zext i32 [[A]] to i64
+; CHECK-NEXT:    call void @use64(i64 [[EXT_WIDE]])
+; CHECK-NEXT:    [[EXT]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT:    br label [[FOR_COND]]
+; CHECK:       for.end:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %a = phi i32 [ %n, %entry ], [ %ext, %for.body ]
+  %cmp = icmp sgt i32 %a, -2
+  br i1 %cmp, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond
+  %ext.wide = zext i32 %a to i64
+  call void @use64(i64 %ext.wide)
+  %ext = trunc i64 %ext.wide to i32
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  ret void
+}
+
+;; Non looping test case.
+define void @test3(i32 %n) {
+; CHECK-LABEL: @test3(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[N:%.*]], -1
+; CHECK-NEXT:    br i1 [[CMP]], label [[BB:%.*]], label [[EXIT:%.*]]
+; CHECK:       bb:
+; CHECK-NEXT:    [[EXT_WIDE:%.*]] = zext nneg i32 [[N]] to i64
+; CHECK-NEXT:    call void @use64(i64 [[EXT_WIDE]])
+; CHECK-NEXT:    [[EXT:%.*]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp = icmp sgt i32 %n, -1
+  br i1 %cmp, label %bb, label %exit
+
+bb:
+  %ext.wide = zext i32 %n to i64
+  call void @use64(i64 %ext.wide)
+  %ext = trunc i64 %ext.wide to i32
+  br label %exit
+
+exit:
+  ret void
+}
+
+;; Non looping negative test case.
+define void @test4(i32 %n) {
+; CHECK-LABEL: @test4(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[N:%.*]], -2
+; CHECK-NEXT:    br i1 [[CMP]], label [[BB:%.*]], label [[EXIT:%.*]]
+; CHECK:       bb:
+; CHECK-NEXT:    [[EXT_WIDE:%.*]] = zext i32 [[N]] to i64
+; CHECK-NEXT:    call void @use64(i64 [[EXT_WIDE]])
+; CHECK-NEXT:    [[EXT:%.*]] = trunc i64 [[EXT_WIDE]] to i32
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %cmp = icmp sgt i32 %n, -2
+  br i1 %cmp, label %bb, label %exit
+
+bb:
+  %ext.wide = zext i32 %n to i64
+  call void @use64(i64 %ext.wide)
+  %ext = trunc i64 %ext.wide to i32
+  br label %exit
+
+exit:
+  ret void
+}
+
+define i64 @may_including_undef(i1 %c.1, i1 %c.2) {
+; CHECK-LABEL: @may_including_undef(
+; CHECK-NEXT:    br i1 [[C_1:%.*]], label [[TRUE_1:%.*]], label [[FALSE:%.*]]
+; CHECK:       true.1:
+; CHECK-NEXT:    br i1 [[C_2:%.*]], label [[TRUE_2:%.*]], label [[EXIT:%.*]]
+; CHECK:       true.2:
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       false:
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[P:%.*]] = phi i32 [ 0, [[TRUE_1]] ], [ 1, [[TRUE_2]] ], [ undef, [[FALSE]] ]
+; CHECK-NEXT:    [[EXT:%.*]] = zext i32 [[P]] to i64
+; CHECK-NEXT:    ret i64 [[EXT]]
+;
+  br i1 %c.1, label %true.1, label %false
+
+true.1:
+  br i1 %c.2, label %true.2, label %exit
+
+true.2:
+  br label %exit
+
+false:
+  br label %exit
+
+exit:
+  %p = phi i32 [ 0, %true.1 ], [ 1, %true.2], [ undef, %false ]
+  %ext = zext i32 %p to i64
+  ret i64 %ext
+}
+
+define i64 @test_infer_at_use(i32 noundef %n) {
----------------
dtcxzyw wrote:

`noundef` is required here.
Alive2: https://alive2.llvm.org/ce/z/ahASB5
See also https://github.com/llvm/llvm-project/commit/1da0da903ee818385d8ce470d14f9f9c7cdf6942

https://github.com/llvm/llvm-project/pull/72052