[llvm-commits] [llvm] r93096 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineCasts.cpp test/Transforms/InstCombine/cast.ll

[Chris Lattner]

Author: lattner
Date: Sat Jan  9 20:22:12 2010
New Revision: 93096

URL: http://llvm.org/viewvc/llvm-project?rev=93096&view=rev
Log:
enhance CanEvaluateZExtd to handle shift left and sext, allowing
more expressions to be promoted and casts eliminated.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
    llvm/trunk/test/Transforms/InstCombine/cast.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp?rev=93096&r1=93095&r2=93096&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp Sat Jan  9 20:22:12 2010
@@ -643,17 +643,31 @@
     if (Tmp1 == -1) return -1;
     Tmp2 = CanEvaluateZExtd(I->getOperand(1), Ty, NumCastsRemoved, TD);
     if (Tmp2 == -1) return -1;
+    return 0; // TODO: Could be improved.
+      
+  case Instruction::Shl:
+    Tmp1 = CanEvaluateZExtd(I->getOperand(0), Ty, NumCastsRemoved, TD);
+    if (Tmp1 == -1) return -1;
+      
+    if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1)))
+      return Tmp1 - CI->getZExtValue();
+
+    // Variable shift, no known zext bits.
+    Tmp2 = CanEvaluateZExtd(I->getOperand(1), Ty, NumCastsRemoved, TD);
+    if (Tmp2 == -1) return -1;
     return 0;
       
-  //case Instruction::Shl:
   //case Instruction::LShr:
   case Instruction::ZExt:
     // zext(zext(x)) -> zext(x).  Since we're replacing it, it isn't eliminated.
     Tmp1 = Ty->getScalarSizeInBits()-OrigTy->getScalarSizeInBits();
     return GetLeadingZeros(I, TD)+Tmp1;
       
-  //case Instruction::SExt:  zext(sext(x)) -> sext(x) with no upper bits known.
-  //case Instruction::Trunc:
+  case Instruction::SExt:
+    // zext(sext(x)) -> sext(x) with no upper bits known.
+    return 0;
+  //case Instruction::Trunc: -> Could turn into AND.
+      
   case Instruction::Select:
     Tmp1 = CanEvaluateZExtd(I->getOperand(1), Ty, NumCastsRemoved, TD);
     if (Tmp1 == -1) return -1;

Modified: llvm/trunk/test/Transforms/InstCombine/cast.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/cast.ll?rev=93096&r1=93095&r2=93096&view=diff

==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/cast.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/cast.ll Sat Jan  9 20:22:12 2010
@@ -403,3 +403,31 @@
 ; CHECK-NEXT: %B = or i64 %A, 1234
 ; CHECK-NEXT: ret i64 %B
 }
+
+define i64 @test45(i8 %A, i64 %Q) {
+ %D = trunc i64 %Q to i32  ;; should be removed
+ %B = sext i8 %A to i32
+ %C = or i32 %B, %D
+ %E = zext i32 %C to i64 
+ ret i64 %E
+; CHECK: @test45
+; CHECK-NEXT: %B = sext i8 %A to i64
+; CHECK-NEXT: %C = or i64 %B, %Q
+; CHECK-NEXT: %E = and i64 %C, 4294967295
+; CHECK-NEXT: ret i64 %E
+}
+
+
+define i64 @test46(i64 %A) {
+ %B = trunc i64 %A to i32
+ %C = and i32 %B, 42
+ %D = shl i32 %C, 8
+ %E = zext i32 %D to i64 
+ ret i64 %E
+; CHECK: @test46
+; CHECK-NEXT: %C = shl i64 %A, 8
+; CHECK-NEXT: %D = and i64 %C, 10752
+; CHECK-NEXT: ret i64 %D
+}
+
+