[llvm-commits] [llvm] r73705 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/trunc-mask-ext.ll

[Dan Gohman]

Author: djg
Date: Thu Jun 18 11:30:21 2009
New Revision: 73705

URL: http://llvm.org/viewvc/llvm-project?rev=73705&view=rev
Log:
Generalize the zext(trunc(t) & C) instcombine to work even with
C is not a low-bits mask, and add a similar instcombine for
zext((trunc(t) & C) ^ C).

Modified:
    llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
    llvm/trunk/test/Transforms/InstCombine/trunc-mask-ext.ll

Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=73705&r1=73704&r2=73705&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Thu Jun 18 11:30:21 2009
@@ -8564,20 +8564,33 @@
     }
   }
 
-  // zext(trunc(t) & C) -> (t & C)  if C is a mask.
+  // zext(trunc(t) & C) -> (t & zext(C)).
   if (SrcI && SrcI->getOpcode() == Instruction::And && SrcI->hasOneUse())
     if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1)))
       if (TruncInst *TI = dyn_cast<TruncInst>(SrcI->getOperand(0))) {
         Value *TI0 = TI->getOperand(0);
-        if (TI0->getType() == CI.getType()) {
-          unsigned TO = C->getValue().countTrailingOnes();
-          if (APIntOps::isMask(TO, C->getValue()))
-            return
-              BinaryOperator::Create(Instruction::And, TI0,
-                                     ConstantExpr::getZExt(C, CI.getType()));
-        }
+        if (TI0->getType() == CI.getType())
+          return
+            BinaryOperator::CreateAnd(TI0,
+                                      ConstantExpr::getZExt(C, CI.getType()));
       }
 
+  // zext((trunc(t) & C) ^ C) -> ((t & zext(C)) ^ zext(C)).
+  if (SrcI && SrcI->getOpcode() == Instruction::Xor && SrcI->hasOneUse())
+    if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1)))
+      if (BinaryOperator *And = dyn_cast<BinaryOperator>(SrcI->getOperand(0)))
+        if (And->getOpcode() == Instruction::And && And->hasOneUse() &&
+            And->getOperand(1) == C)
+          if (TruncInst *TI = dyn_cast<TruncInst>(And->getOperand(0))) {
+            Value *TI0 = TI->getOperand(0);
+            if (TI0->getType() == CI.getType()) {
+              Constant *ZC = ConstantExpr::getZExt(C, CI.getType());
+              Instruction *NewAnd = BinaryOperator::CreateAnd(TI0, ZC, "tmp");
+              InsertNewInstBefore(NewAnd, *And);
+              return BinaryOperator::CreateXor(NewAnd, ZC);
+            }
+          }
+
   return 0;
 }
 

Modified: llvm/trunk/test/Transforms/InstCombine/trunc-mask-ext.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/trunc-mask-ext.ll?rev=73705&r1=73704&r2=73705&view=diff

==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/trunc-mask-ext.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/trunc-mask-ext.ll Thu Jun 18 11:30:21 2009
@@ -2,7 +2,7 @@
 ; RUN: not grep zext %t
 ; RUN: not grep sext %t
 
-; Instcombine should be able to eliminate both ext casts.
+; Instcombine should be able to eliminate all of these ext casts.
 
 declare void @use(i32)
 
@@ -21,3 +21,18 @@
   call void @use(i32 %b)
   ret i64 %d
 }
+define i64 @goo(i64 %a) {
+  %b = trunc i64 %a to i32
+  %c = and i32 %b, 8
+  %d = zext i32 %c to i64
+  call void @use(i32 %b)
+  ret i64 %d
+}
+define i64 @hoo(i64 %a) {
+  %b = trunc i64 %a to i32
+  %c = and i32 %b, 8
+  %x = xor i32 %c, 8
+  %d = zext i32 %x to i64
+  call void @use(i32 %b)
+  ret i64 %d
+}