[PATCH] D151541: [ValueTracking] Implied conditions for lshr

[Joshua Cao via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGcb9f1aaddac0: [ValueTracking] Implied conditions for lshr (authored by caojoshua).

Changed prior to commit:
  https://reviews.llvm.org/D151541?vs=525972&id=529148#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D151541/new/

https://reviews.llvm.org/D151541

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/test/Transforms/InstSimplify/implies.ll


Index: llvm/test/Transforms/InstSimplify/implies.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/implies.ll
+++ llvm/test/Transforms/InstSimplify/implies.ll
@@ -449,9 +449,8 @@
 ; CHECK-LABEL: @test_shift(
 ; CHECK-NEXT:    [[LSHR:%.*]] = lshr i64 [[X:%.*]], [[SHIFT:%.*]]
 ; CHECK-NEXT:    [[ICMP1:%.*]] = icmp ugt i64 [[LSHR]], [[Y:%.*]]
-; CHECK-NEXT:    [[ICMP2:%.*]] = icmp ugt i64 [[X]], [[Y]]
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[ICMP1]])
-; CHECK-NEXT:    ret i1 [[ICMP2]]
+; CHECK-NEXT:    ret i1 true
 ;
   %lshr = lshr i64 %x, %shift
   %icmp1 = icmp ugt i64 %lshr, %y
@@ -479,11 +478,7 @@
 ; i <u L ==> i >> C <u L
 define i1 @lshr_constant(i32 %length.i, i32 %i) {
 ; CHECK-LABEL: @lshr_constant(
-; CHECK-NEXT:    [[SHL:%.*]] = lshr i32 [[I:%.*]], 1
-; CHECK-NEXT:    [[VAR29:%.*]] = icmp ult i32 [[I]], [[LENGTH_I:%.*]]
-; CHECK-NEXT:    [[VAR30:%.*]] = icmp ult i32 [[SHL]], [[LENGTH_I]]
-; CHECK-NEXT:    [[RES:%.*]] = icmp ule i1 [[VAR29]], [[VAR30]]
-; CHECK-NEXT:    ret i1 [[RES]]
+; CHECK-NEXT:    ret i1 true
 ;
   %shl = lshr i32 %i, 1
   %var29 = icmp ult i32 %i, %length.i
@@ -495,11 +490,7 @@
 ; i <u L ==> i >> V <u L
 define i1 @lshr_value(i32 %length.i, i32 %i, i32 %v) {
 ; CHECK-LABEL: @lshr_value(
-; CHECK-NEXT:    [[SHL:%.*]] = lshr i32 [[I:%.*]], [[V:%.*]]
-; CHECK-NEXT:    [[VAR29:%.*]] = icmp ult i32 [[I]], [[LENGTH_I:%.*]]
-; CHECK-NEXT:    [[VAR30:%.*]] = icmp ult i32 [[SHL]], [[LENGTH_I]]
-; CHECK-NEXT:    [[RES:%.*]] = icmp ule i1 [[VAR29]], [[VAR30]]
-; CHECK-NEXT:    ret i1 [[RES]]
+; CHECK-NEXT:    ret i1 true
 ;
   %shl = lshr i32 %i, %v
   %var29 = icmp ult i32 %i, %length.i
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -7913,6 +7913,10 @@
     if (match(RHS, m_NUWAdd(m_Specific(LHS), m_APInt(C))))
       return true;
 
+    // RHS >> V u<= RHS for any V
+    if (match(LHS, m_LShr(m_Specific(RHS), m_Value())))
+      return true;
+
     // Match A to (X +_{nuw} CA) and B to (X +_{nuw} CB)
     auto MatchNUWAddsToSameValue = [&](const Value *A, const Value *B,
                                        const Value *&X,


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