InstCombine: FoldOrOfICmps harder

We may be in a situation where the icmps might not be near each other in
a tree of or instructions.  Try to dig out related compare instructions
and see if they combine.

N.B.  This won't fire on deep trees of compares because rewritting the
tree might end up creating a net increase of IR.  We may have to resort
to something more sophisticated if this is a real problem.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222928 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 55ebcedf9440c40c49fdaa029d91f3c015a27d45..60b859fc149dfbdb0e3d694b886059e4c9c9a734 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2305,11 +2305,34 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
   if (SwappedForXor)
     std::swap(Op0, Op1);
 
-  if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1)))
-    if (ICmpInst *LHS = dyn_cast<ICmpInst>(I.getOperand(0)))
+  {
+    ICmpInst *LHS = dyn_cast<ICmpInst>(Op0);
+    ICmpInst *RHS = dyn_cast<ICmpInst>(Op1);
+    if (LHS && RHS)
       if (Value *Res = FoldOrOfICmps(LHS, RHS, &I))
         return ReplaceInstUsesWith(I, Res);
 
+    // TODO: Make this recursive; it's a little tricky because an arbitrary
+    // number of 'or' instructions might have to be created.
+    Value *X, *Y;
+    if (LHS && match(Op1, m_OneUse(m_Or(m_Value(X), m_Value(Y))))) {
+      if (auto *Cmp = dyn_cast<ICmpInst>(X))
+        if (Value *Res = FoldOrOfICmps(LHS, Cmp, &I))
+          return ReplaceInstUsesWith(I, Builder->CreateOr(Res, Y));
+      if (auto *Cmp = dyn_cast<ICmpInst>(Y))
+        if (Value *Res = FoldOrOfICmps(LHS, Cmp, &I))
+          return ReplaceInstUsesWith(I, Builder->CreateOr(Res, X));
+    }
+    if (RHS && match(Op0, m_OneUse(m_Or(m_Value(X), m_Value(Y))))) {
+      if (auto *Cmp = dyn_cast<ICmpInst>(X))
+        if (Value *Res = FoldOrOfICmps(Cmp, RHS, &I))
+          return ReplaceInstUsesWith(I, Builder->CreateOr(Res, Y));
+      if (auto *Cmp = dyn_cast<ICmpInst>(Y))
+        if (Value *Res = FoldOrOfICmps(Cmp, RHS, &I))
+          return ReplaceInstUsesWith(I, Builder->CreateOr(Res, X));
+    }
+  }
+
   // (fcmp uno x, c) | (fcmp uno y, c)  -> (fcmp uno x, y)
   if (FCmpInst *LHS = dyn_cast<FCmpInst>(I.getOperand(0)))
     if (FCmpInst *RHS = dyn_cast<FCmpInst>(I.getOperand(1)))

diff --git a/test/Transforms/InstCombine/or.ll b/test/Transforms/InstCombine/or.ll
index 23dad212e4788512f265699a9d7c0d096e761a0f..f604bafcc3302ce43cc28bc3db1e88f807ba4eec 100644 (file)
--- a/test/Transforms/InstCombine/or.ll
+++ b/test/Transforms/InstCombine/or.ll
@@ -506,3 +506,13 @@ define i1 @test47(i8 signext %c)  {
 ; CHECK-NEXT:  add i8 %1, -65
 ; CHECK-NEXT:  icmp ult i8 %2, 27
 }
+
+define i1 @test48(i64 %x, i1 %b) {
+  %1 = icmp ult i64 %x, 2305843009213693952
+  %2 = icmp ugt i64 %x, 2305843009213693951
+  %.b = or i1 %2, %b
+  %3 = or i1 %1, %.b
+  ret i1 %3
+; CHECK-LABEL: @test48(
+; CHECK-NEXT:  ret i1 true
+}