[llvm-commits] [llvm] r162743 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp test/Transforms/InstCombine/2012-08-28-udiv_ashl.ll test/Transforms/InstCombine/udiv-simplify-bug-1.ll

[Benjamin Kramer]

On 28.08.2012, at 12:01, Nadav Rotem <nrotem at apple.com> wrote:

> Author: nadav
> Date: Tue Aug 28 05:01:43 2012
> New Revision: 162743
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=162743&view=rev
> Log:
> 
> Teach InstCombine to canonicalize  [SU]div+[AL]shl patterns.
> 
> For example:
>  %1 = lshr i32 %x, 2
>  %2 = udiv i32 %1, 100
> 
> rdar://12182093
> 
> 
> 
> Added:
>    llvm/trunk/test/Transforms/InstCombine/2012-08-28-udiv_ashl.ll
> Modified:
>    llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
>    llvm/trunk/test/Transforms/InstCombine/udiv-simplify-bug-1.ll
> 
> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp?rev=162743&r1=162742&r2=162743&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp (original)
> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp Tue Aug 28 05:01:43 2012
> @@ -462,6 +462,16 @@
>     }
>   }
> 
> +  // Udiv ((Lshl x, c1) , c2) ->  x / (C1 * 1<<C2);
> +  if (Constant *C = dyn_cast<Constant>(Op1)) {
> +    Value *X = 0, *C1 = 0;
> +    if (match(Op0, m_LShr(m_Value(X), m_Value(C1)))) {
> +      uint64_t NC = cast<ConstantInt>(C)->getZExtValue() *
> +                    (1<< cast<ConstantInt>(C1)->getZExtValue());

This will crash for bit widths > 64, you can use APInt arithmetic instead to make it work for big integers.

> +      return BinaryOperator::CreateUDiv(X, ConstantInt::get(I.getType(), NC));
> +    }
> +  }
> +
>   // X udiv (C1 << N), where C1 is "1<<C2"  -->  X >> (N+C2)
>   { const APInt *CI; Value *N;
>     if (match(Op1, m_Shl(m_Power2(CI), m_Value(N))) ||
> @@ -533,6 +543,16 @@
>                                           ConstantExpr::getNeg(RHS));
>   }
> 
> +  // Sdiv ((Ashl x, c1) , c2) ->  x / (C1 * 1<<C2);
> +  if (Constant *C = dyn_cast<Constant>(Op1)) {
> +    Value *X = 0, *C1 = 0;
> +    if (match(Op0, m_AShr(m_Value(X), m_Value(C1)))) {
> +      uint64_t NC = cast<ConstantInt>(C)->getZExtValue() *
> +                    (1<< cast<ConstantInt>(C1)->getZExtValue());

ditto

- Ben

> +      return BinaryOperator::CreateSDiv(X, ConstantInt::get(I.getType(), NC));
> +    }
> +  }
> +
>   // If the sign bits of both operands are zero (i.e. we can prove they are
>   // unsigned inputs), turn this into a udiv.
>   if (I.getType()->isIntegerTy()) {
> 
> Added: llvm/trunk/test/Transforms/InstCombine/2012-08-28-udiv_ashl.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/2012-08-28-udiv_ashl.ll?rev=162743&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/2012-08-28-udiv_ashl.ll (added)
> +++ llvm/trunk/test/Transforms/InstCombine/2012-08-28-udiv_ashl.ll Tue Aug 28 05:01:43 2012
> @@ -0,0 +1,50 @@
> +; RUN: opt -S -instcombine < %s | FileCheck %s
> +
> +; rdar://12182093
> +
> +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
> +target triple = "x86_64-apple-macosx10.8.0"
> +
> +; CHECK: @udiv400
> +; CHECK: udiv i32 %x, 400
> +; CHECK: ret
> +define i32 @udiv400(i32 %x) {
> +entry:
> +  %div = lshr i32 %x, 2
> +  %div1 = udiv i32 %div, 100
> +  ret i32 %div1
> +}
> +
> +; CHECK: @sdiv400
> +; CHECK: sdiv i32 %x, 400
> +; CHECK: ret
> +define i32 @sdiv400(i32 %x) {
> +entry:
> +  %div = ashr i32 %x, 2
> +  %div1 = sdiv i32 %div, 100
> +  ret i32 %div1
> +}
> +
> +; CHECK: @udiv400_no
> +; CHECK: ashr
> +; CHECK: div
> +; CHECK: ret
> +define i32 @udiv400_no(i32 %x) {
> +entry:
> +  %div = ashr i32 %x, 2
> +  %div1 = udiv i32 %div, 100
> +  ret i32 %div1
> +}
> +
> +; CHECK: @sdiv400_yes
> +; CHECK: udiv i32 %x, 400
> +; CHECK: ret
> +define i32 @sdiv400_yes(i32 %x) {
> +entry:
> +  %div = lshr i32 %x, 2
> +  ; The sign bits of both operands are zero (i.e. we can prove they are
> +  ; unsigned inputs), turn this into a udiv.
> +  ; Next, optimize this just like sdiv.
> +  %div1 = sdiv i32 %div, 100
> +  ret i32 %div1
> +}
> 
> Modified: llvm/trunk/test/Transforms/InstCombine/udiv-simplify-bug-1.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/udiv-simplify-bug-1.ll?rev=162743&r1=162742&r2=162743&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/udiv-simplify-bug-1.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/udiv-simplify-bug-1.ll Tue Aug 28 05:01:43 2012
> @@ -6,9 +6,9 @@
> ; The udiv instructions shouldn't be optimized away, and the
> ; sext instructions should be optimized to zext.
> 
> -define i64 @bar(i32 %x) nounwind {
> +define i64 @bar(i32 %x, i32 %g) nounwind {
>   %y = lshr i32 %x, 30
> -  %r = udiv i32 %y, 3
> +  %r = udiv i32 %y, %g
>   %z = sext i32 %r to i64
>   ret i64 %z
> }
> 
> 
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