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llvm-6502/test/Transforms/InstCombine/overflow-mul.ll
Serge Pavlov ea0ea63773 Recognize test for overflow in integer multiplication. 
If multiplication involves zero-extended arguments and the result is
compared as in the patterns:

    %mul32 = trunc i64 %mul64 to i32
    %zext = zext i32 %mul32 to i64
    %overflow = icmp ne i64 %mul64, %zext
or
    %overflow = icmp ugt i64 %mul64 , 0xffffffff

then the multiplication may be replaced by call to umul.with.overflow.
This change fixes PR4917 and PR4918.

Differential Revision: http://llvm-reviews.chandlerc.com/D2814


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206137 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-13 18:23:41 +00:00

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; RUN: opt -S -instcombine < %s | FileCheck %s
; return mul(zext x, zext y) > MAX
define i32 @pr4917_1(i32 %x, i32 %y) nounwind {
; CHECK-LABEL: @pr4917_1(
entry:
%l = zext i32 %x to i64
%r = zext i32 %y to i64
; CHECK-NOT: zext i32
%mul64 = mul i64 %l, %r
; CHECK: [[MUL:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %x, i32 %y)
%overflow = icmp ugt i64 %mul64, 4294967295
; CHECK: extractvalue { i32, i1 } [[MUL]], 1
%retval = zext i1 %overflow to i32
ret i32 %retval
}
; return mul(zext x, zext y) >= MAX+1
define i32 @pr4917_1a(i32 %x, i32 %y) nounwind {
; CHECK-LABEL: @pr4917_1a(
entry:
%l = zext i32 %x to i64
%r = zext i32 %y to i64
; CHECK-NOT: zext i32
%mul64 = mul i64 %l, %r
; CHECK: [[MUL:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %x, i32 %y)
%overflow = icmp uge i64 %mul64, 4294967296
; CHECK: extractvalue { i32, i1 } [[MUL]], 1
%retval = zext i1 %overflow to i32
ret i32 %retval
}
; mul(zext x, zext y) > MAX
; mul(x, y) is used
define i32 @pr4917_2(i32 %x, i32 %y) nounwind {
; CHECK-LABEL: @pr4917_2(
entry:
%l = zext i32 %x to i64
%r = zext i32 %y to i64
; CHECK-NOT: zext i32
%mul64 = mul i64 %l, %r
; CHECK: [[MUL:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %x, i32 %y)
%overflow = icmp ugt i64 %mul64, 4294967295
; CHECK-DAG: [[VAL:%.*]] = extractvalue { i32, i1 } [[MUL]], 0
%mul32 = trunc i64 %mul64 to i32
; CHECK-DAG: [[OVFL:%.*]] = extractvalue { i32, i1 } [[MUL]], 1
%retval = select i1 %overflow, i32 %mul32, i32 111
; CHECK: select i1 [[OVFL]], i32 [[VAL]]
ret i32 %retval
}
; return mul(zext x, zext y) > MAX
; mul is used in non-truncate
define i64 @pr4917_3(i32 %x, i32 %y) nounwind {
; CHECK-LABEL: @pr4917_3(
entry:
%l = zext i32 %x to i64
%r = zext i32 %y to i64
%mul64 = mul i64 %l, %r
; CHECK-NOT: umul.with.overflow.i32
%overflow = icmp ugt i64 %mul64, 4294967295
%retval = select i1 %overflow, i64 %mul64, i64 111
ret i64 %retval
}
; return mul(zext x, zext y) <= MAX
define i32 @pr4917_4(i32 %x, i32 %y) nounwind {
; CHECK-LABEL: @pr4917_4(
entry:
%l = zext i32 %x to i64
%r = zext i32 %y to i64
; CHECK-NOT: zext i32
%mul64 = mul i64 %l, %r
; CHECK: [[MUL:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %x, i32 %y)
%overflow = icmp ule i64 %mul64, 4294967295
; CHECK: extractvalue { i32, i1 } [[MUL]], 1
; CHECK: xor
%retval = zext i1 %overflow to i32
ret i32 %retval
}
; return mul(zext x, zext y) < MAX+1
define i32 @pr4917_4a(i32 %x, i32 %y) nounwind {
; CHECK-LABEL: @pr4917_4a(
entry:
%l = zext i32 %x to i64
%r = zext i32 %y to i64
; CHECK-NOT: zext i32
%mul64 = mul i64 %l, %r
; CHECK: [[MUL:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %x, i32 %y)
%overflow = icmp ult i64 %mul64, 4294967296
; CHECK: extractvalue { i32, i1 } [[MUL]], 1
; CHECK: xor
%retval = zext i1 %overflow to i32
ret i32 %retval
}
; operands of mul are of different size
define i32 @pr4917_5(i32 %x, i8 %y) nounwind {
; CHECK-LABEL: @pr4917_5(
entry:
%l = zext i32 %x to i64
%r = zext i8 %y to i64
; CHECK: [[Y:%.*]] = zext i8 %y to i32
%mul64 = mul i64 %l, %r
%overflow = icmp ugt i64 %mul64, 4294967295
%mul32 = trunc i64 %mul64 to i32
; CHECK: [[MUL:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %x, i32 [[Y]])
; CHECK-DAG: [[VAL:%.*]] = extractvalue { i32, i1 } [[MUL]], 0
; CHECK-DAG: [[OVFL:%.*]] = extractvalue { i32, i1 } [[MUL]], 1
%retval = select i1 %overflow, i32 %mul32, i32 111
; CHECK: select i1 [[OVFL]], i32 [[VAL]]
ret i32 %retval
}
; mul(zext x, zext y) != zext trunc mul
define i32 @pr4918_1(i32 %x, i32 %y) nounwind {
; CHECK-LABEL: @pr4918_1(
entry:
%l = zext i32 %x to i64
%r = zext i32 %y to i64
%mul64 = mul i64 %l, %r
; CHECK: [[MUL:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %x, i32 %y)
%part32 = trunc i64 %mul64 to i32
%part64 = zext i32 %part32 to i64
%overflow = icmp ne i64 %mul64, %part64
; CHECK: [[OVFL:%.*]] = extractvalue { i32, i1 } [[MUL:%.*]], 1
%retval = zext i1 %overflow to i32
ret i32 %retval
}
; mul(zext x, zext y) == zext trunc mul
define i32 @pr4918_2(i32 %x, i32 %y) nounwind {
; CHECK-LABEL: @pr4918_2(
entry:
%l = zext i32 %x to i64
%r = zext i32 %y to i64
%mul64 = mul i64 %l, %r
; CHECK: [[MUL:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %x, i32 %y)
%part32 = trunc i64 %mul64 to i32
%part64 = zext i32 %part32 to i64
%overflow = icmp eq i64 %mul64, %part64
; CHECK: extractvalue { i32, i1 } [[MUL]]
%retval = zext i1 %overflow to i32
; CHECK: xor
ret i32 %retval
}
; zext trunc mul != mul(zext x, zext y)
define i32 @pr4918_3(i32 %x, i32 %y) nounwind {
; CHECK-LABEL: @pr4918_3(
entry:
%l = zext i32 %x to i64
%r = zext i32 %y to i64
%mul64 = mul i64 %l, %r
; CHECK: [[MUL:%.*]] = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %x, i32 %y)
%part32 = trunc i64 %mul64 to i32
%part64 = zext i32 %part32 to i64
%overflow = icmp ne i64 %part64, %mul64
; CHECK: extractvalue { i32, i1 } [[MUL]], 1
%retval = zext i1 %overflow to i32
ret i32 %retval
}
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