[PATCH] D85092: [InstSimplify] Peephole optimization for icmp (urem X, Y), X

[Xavier Denis via Phabricator via llvm-commits]

xldenis updated this revision to Diff 282448.
xldenis added a comment.

Rebase patch on latest master.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D85092/new/

https://reviews.llvm.org/D85092

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstSimplify/compare.ll


Index: llvm/test/Transforms/InstSimplify/compare.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/compare.ll
+++ llvm/test/Transforms/InstSimplify/compare.ll
@@ -723,6 +723,40 @@
   ret i1 %B
 }
 
+define i1 @urem8(i8 %X, i8 %Y) {
+; CHECK-LABEL: @urem8(
+; CHECK-NEXT: ret i1 true
+;
+  %A = urem i8 %X, %Y
+  %B = icmp ule i8 %A, %Y
+  ret i1 %B
+}
+
+define i1 @urem9(i8 %X, i8 %Y) {
+  ; CHECK-LABEL: @urem9(
+  ; CHECK-NEXT: ret i1 false
+  ;
+  %A = urem i8 %X, %Y
+  %B = icmp ugt i8 %A, %Y
+  ret i1 %B
+}
+
+define i1 @urem10(i8 %X, i8 %Y) {
+  ; CHECK-LABEL: @urem10(
+  ; CHECK-NEXT: ret i1 false
+  %A = urem i8 %X, %Y
+  %B = icmp ule i8 %Y, %A
+  ret i1 %B
+}
+
+define i1 @urem11(i8 %X, i8 %Y) {
+  ; CHECK-LABEL: @urem11(
+  ; CHECK-NEXT: ret i1 true
+  %A = urem i8 %X, %Y
+  %B = icmp ugt i8 %Y, %A
+  ret i1 %B
+}
+
 ; PR9343 #15
 define i1 @srem2(i16 %X, i32 %Y) {
 ; CHECK-LABEL: @srem2(
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -2814,6 +2814,14 @@
     }
   }
 
+  // icmp pred (urem Y, X), Y
+  if (LBO && match(LBO, m_URem(m_Specific(RHS), m_Value()))) {
+    if (Pred == ICmpInst::ICMP_ULE)
+      return getTrue(ITy);
+    if (Pred == ICmpInst::ICMP_UGT)
+      return getFalse(ITy);
+  }
+
   // x >> y <=u x
   // x udiv y <=u x.
   if (match(LBO, m_LShr(m_Specific(RHS), m_Value())) ||


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