[llvm-commits] [llvm] r73656 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/trunc-mask-ext.ll

[Dan Gohman]

Author: djg
Date: Wed Jun 17 18:17:05 2009
New Revision: 73656

URL: http://llvm.org/viewvc/llvm-project?rev=73656&view=rev
Log:
Instcombine zext(trunc(x) & mask) to x&mask, even if the trunc has
multiple users.

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

Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=73656&r1=73655&r2=73656&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Wed Jun 17 18:17:05 2009
@@ -8564,6 +8564,20 @@
     }
   }
 
+  // zext(trunc(t) & C) -> (t & C)  if C is a mask.
+  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()));
+        }
+      }
+
   return 0;
 }
 

Added: 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=73656&view=auto

==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/trunc-mask-ext.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/trunc-mask-ext.ll Wed Jun 17 18:17:05 2009
@@ -0,0 +1,23 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis > %t
+; RUN: not grep zext %t
+; RUN: not grep sext %t
+
+; Instcombine should be able to eliminate both ext casts.
+
+declare void @use(i32)
+
+define i64 @foo(i64 %a) {
+  %b = trunc i64 %a to i32
+  %c = and i32 %b, 15
+  %d = zext i32 %c to i64
+  call void @use(i32 %b)
+  ret i64 %d
+}
+define i64 @bar(i64 %a) {
+  %b = trunc i64 %a to i32
+  %c = shl i32 %b, 4
+  %q = ashr i32 %c, 4
+  %d = sext i32 %q to i64
+  call void @use(i32 %b)
+  ret i64 %d
+}