[PATCH] D111180: The result of a function with noundef return attribute must be well defined

[Philip Reames via Phabricator via llvm-commits]

reames updated this revision to Diff 377622.
reames added a comment.

Add tests - key detail is that removing udiv no-longer has any effect as noimplicit defs serves as a immediate UB root.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D111180/new/

https://reviews.llvm.org/D111180

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/test/Analysis/ScalarEvolution/flags-from-poison.ll


Index: llvm/test/Analysis/ScalarEvolution/flags-from-poison.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/flags-from-poison.ll
+++ llvm/test/Analysis/ScalarEvolution/flags-from-poison.ll
@@ -1621,21 +1621,15 @@
   br label %for.cond
 }
 
-; TODO: once D111180 lands, remove the udiv from these *-basic tests.
-; noundef really should be enough
-
 define noundef i32 @add-basic(i32 %a, i32 %b) {
 ; CHECK-LABEL: 'add-basic'
 ; CHECK-NEXT:  Classifying expressions for: @add-basic
 ; CHECK-NEXT:    %res = add nuw nsw i32 %a, %b
 ; CHECK-NEXT:    --> (%a + %b)<nuw><nsw> U: full-set S: full-set
-; CHECK-NEXT:    %res2 = udiv i32 255, %res
-; CHECK-NEXT:    --> (255 /u (%a + %b)<nuw><nsw>) U: [0,256) S: [0,256)
 ; CHECK-NEXT:  Determining loop execution counts for: @add-basic
 ;
   %res = add nuw nsw i32 %a, %b
-  %res2 = udiv i32 255, %res
-  ret i32 %res2
+  ret i32 %res
 }
 
 define noundef i32 @sub-basic(i32 %a, i32 %b) {
@@ -1643,13 +1637,10 @@
 ; CHECK-NEXT:  Classifying expressions for: @sub-basic
 ; CHECK-NEXT:    %res = sub nuw nsw i32 %a, %b
 ; CHECK-NEXT:    --> ((-1 * %b) + %a) U: full-set S: full-set
-; CHECK-NEXT:    %res2 = udiv i32 255, %res
-; CHECK-NEXT:    --> (255 /u ((-1 * %b) + %a)) U: [0,256) S: [0,256)
 ; CHECK-NEXT:  Determining loop execution counts for: @sub-basic
 ;
   %res = sub nuw nsw i32 %a, %b
-  %res2 = udiv i32 255, %res
-  ret i32 %res2
+  ret i32 %res
 }
 
 define noundef i32 @mul-basic(i32 %a, i32 %b) {
@@ -1657,13 +1648,10 @@
 ; CHECK-NEXT:  Classifying expressions for: @mul-basic
 ; CHECK-NEXT:    %res = mul nuw nsw i32 %a, %b
 ; CHECK-NEXT:    --> (%a * %b)<nuw><nsw> U: full-set S: full-set
-; CHECK-NEXT:    %res2 = udiv i32 255, %res
-; CHECK-NEXT:    --> (255 /u (%a * %b)<nuw><nsw>) U: [0,256) S: [0,256)
 ; CHECK-NEXT:  Determining loop execution counts for: @mul-basic
 ;
   %res = mul nuw nsw i32 %a, %b
-  %res2 = udiv i32 255, %res
-  ret i32 %res2
+  ret i32 %res
 }
 
 @gA = external global i32
@@ -1746,9 +1734,9 @@
 ; CHECK-NEXT:    %d = load i32, i32* @gD, align 4
 ; CHECK-NEXT:    --> %d U: full-set S: full-set
 ; CHECK-NEXT:    %x = mul nuw i32 %a, %b
-; CHECK-NEXT:    --> (%a * %b) U: full-set S: full-set
+; CHECK-NEXT:    --> (%a * %b)<nuw> U: full-set S: full-set
 ; CHECK-NEXT:    %y = mul nuw i32 %c, %d
-; CHECK-NEXT:    --> (%c * %d) U: full-set S: full-set
+; CHECK-NEXT:    --> (%c * %d)<nuw> U: full-set S: full-set
 ; CHECK-NEXT:    %res = mul nuw i32 %x, %y
 ; CHECK-NEXT:    --> (%a * %b * %c * %d) U: full-set S: full-set
 ; CHECK-NEXT:  Determining loop execution counts for: @mul-recurse
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -5418,7 +5418,10 @@
       }
       break;
     }
-
+    case Instruction::Ret:
+      if (I->getFunction()->hasRetAttribute(Attribute::NoUndef))
+        Operands.insert(I->getOperand(0));
+      break;
     default:
       break;
   }


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