aggressive changed the canonical form from sext(trunc(x)) to ashr(lshr(x)),
make sure to transform a couple more things into that canonical form,
and catch a case where we missed turning zext/shl/ashr into a single sext.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93787
91177308-0d34-0410-b5e6-
96231b3b80d8
ShAmt);
}
+ // If this input is a trunc from our destination, then turn sext(trunc(x))
+ // into shifts.
+ if (TruncInst *TI = dyn_cast<TruncInst>(Src))
+ if (TI->hasOneUse() && TI->getOperand(0)->getType() == DestTy) {
+ uint32_t SrcBitSize = SrcTy->getScalarSizeInBits();
+ uint32_t DestBitSize = DestTy->getScalarSizeInBits();
+
+ // We need to emit a shl + ashr to do the sign extend.
+ Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize);
+ Value *Res = Builder->CreateShl(TI->getOperand(0), ShAmt, "sext");
+ return BinaryOperator::CreateAShr(Res, ShAmt);
+ }
+
// If the input is a shl/ashr pair of a same constant, then this is a sign
// extension from a smaller value. If we could trust arbitrary bitwidth
// integers, we could turn this into a truncate to the smaller bit and then
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
// If the input is a SHL by the same constant (ashr (shl X, C), C), then we
- // have a sign-extend idiom. If the input value is known to already be sign
- // extended enough, delete the extension.
+ // have a sign-extend idiom.
Value *X;
- if (match(Op0, m_Shl(m_Value(X), m_Specific(Op1))) &&
- ComputeNumSignBits(X) > Op1C->getZExtValue())
- return ReplaceInstUsesWith(I, X);
+ if (match(Op0, m_Shl(m_Value(X), m_Specific(Op1)))) {
+ // If the input value is known to already be sign extended enough, delete
+ // the extension.
+ if (ComputeNumSignBits(X) > Op1C->getZExtValue())
+ return ReplaceInstUsesWith(I, X);
+
+ // If the input is an extension from the shifted amount value, e.g.
+ // %x = zext i8 %A to i32
+ // %y = shl i32 %x, 24
+ // %z = ashr %y, 24
+ // then turn this into "z = sext i8 A to i32".
+ if (ZExtInst *ZI = dyn_cast<ZExtInst>(X)) {
+ uint32_t SrcBits = ZI->getOperand(0)->getType()->getScalarSizeInBits();
+ uint32_t DestBits = ZI->getType()->getScalarSizeInBits();
+ if (Op1C->getZExtValue() == DestBits-SrcBits)
+ return new SExtInst(ZI->getOperand(0), ZI->getType());
+ }
+ }
}
// See if we can turn a signed shr into an unsigned shr.
%tmp.3 = add i32 %tmp.2, 32768 ; <i32> [#uses=1]
ret i32 %tmp.3
; CHECK: @test1
-; CHECK: %sext = trunc i32 %x to i16
-; CHECK: %tmp.3 = sext i16 %sext to i32
+; CHECK: %sext1 = shl i32 %x, 16
+; CHECK: %tmp.3 = ashr i32 %sext1, 16
; CHECK: ret i32 %tmp.3
}
%tmp.3 = add i32 %tmp.2, -32768 ; <i32> [#uses=1]
ret i32 %tmp.3
; CHECK: @test2
-; CHECK: %sext = trunc i32 %x to i16
-; CHECK: %tmp.3 = sext i16 %sext to i32
+; CHECK: %sext1 = shl i32 %x, 16
+; CHECK: %tmp.3 = ashr i32 %sext1, 16
; CHECK: ret i32 %tmp.3
}
%tmp.3 = add i32 %tmp.2, -128 ; <i32> [#uses=1]
ret i32 %tmp.3
; CHECK: @test5
-; CHECK: %sext = trunc i32 %x to i8
-; CHECK: %tmp.3 = sext i8 %sext to i32
+; CHECK: %sext1 = shl i32 %x, 24
+; CHECK: %tmp.3 = ashr i32 %sext1, 24
; CHECK: ret i32 %tmp.3
}
; CHECK: ret i32 %tmp.4
}
+define i32 @test7(i16 %P) {
+ %tmp.1 = zext i16 %P to i32 ; <i32> [#uses=1]
+ %sext1 = shl i32 %tmp.1, 16 ; <i32> [#uses=1]
+ %tmp.5 = ashr i32 %sext1, 16 ; <i32> [#uses=1]
+ ret i32 %tmp.5
+; CHECK: @test7
+; CHECK: %tmp.5 = sext i16 %P to i32
+; CHECK: ret i32 %tmp.5
+}