[llvm] r354393 - [InstCombine] reduce even more unsigned saturated add with 'not' op
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Tue Feb 19 14:14:22 PST 2019
Author: spatel
Date: Tue Feb 19 14:14:21 2019
New Revision: 354393
URL: http://llvm.org/viewvc/llvm-project?rev=354393&view=rev
Log:
[InstCombine] reduce even more unsigned saturated add with 'not' op
We want to use the sum in the icmp to allow matching with
m_UAddWithOverflow and eliminate the 'not'. This is discussed
in D51929 and is another step towards solving PR14613:
https://bugs.llvm.org/show_bug.cgi?id=14613
Name: uaddsat, -1 fval
%notx = xor i32 %x, -1
%a = add i32 %x, %y
%c = icmp ugt i32 %notx, %y
%r = select i1 %c, i32 %a, i32 -1
=>
%a = add i32 %x, %y
%c2 = icmp ugt i32 %y, %a
%r = select i1 %c2, i32 -1, i32 %a
Name: uaddsat, -1 fval + ult
%notx = xor i32 %x, -1
%a = add i32 %x, %y
%c = icmp ult i32 %y, %notx
%r = select i1 %c, i32 %a, i32 -1
=>
%a = add i32 %x, %y
%c2 = icmp ugt i32 %y, %a
%r = select i1 %c2, i32 -1, i32 %a
https://rise4fun.com/Alive/nTp
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
llvm/trunk/test/Transforms/InstCombine/saturating-add-sub.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp?rev=354393&r1=354392&r2=354393&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp Tue Feb 19 14:14:21 2019
@@ -695,22 +695,30 @@ static Value *canonicalizeSaturatedAdd(I
return Builder.CreateSelect(NewCmp, FVal, TVal);
}
- // Canonicalize to 'ULT' to simplify matching below.
+ // Match unsigned saturated add of 2 variables with an unnecessary 'not'.
+ // There are 8 commuted variants.
+ // Canonicalize -1 (saturated result) to true value of the select.
+ if (match(FVal, m_AllOnes())) {
+ std::swap(TVal, FVal);
+ std::swap(Cmp0, Cmp1);
+ }
+ if (!match(TVal, m_AllOnes()))
+ return nullptr;
+
+ // Canonicalize predicate to 'ULT'.
if (Pred == ICmpInst::ICMP_UGT) {
Pred = ICmpInst::ICMP_ULT;
std::swap(Cmp0, Cmp1);
}
-
if (Pred != ICmpInst::ICMP_ULT)
return nullptr;
// Match unsigned saturated add of 2 variables with an unnecessary 'not'.
- // TODO: There are more variations of this pattern.
Value *Y;
- if (match(TVal, m_AllOnes()) && match(Cmp0, m_Not(m_Value(X))) &&
+ if (match(Cmp0, m_Not(m_Value(X))) &&
match(FVal, m_c_Add(m_Specific(X), m_Value(Y))) && Y == Cmp1) {
// Change the comparison to use the sum (false value of the select). That is
- // the canonical pattern match form for uadd.with.overflow and eliminates a
+ // a canonical pattern match form for uadd.with.overflow and eliminates a
// use of the 'not' op:
// (~X u< Y) ? -1 : (X + Y) --> ((X + Y) u< Y) ? -1 : (X + Y)
// (~X u< Y) ? -1 : (Y + X) --> ((Y + X) u< Y) ? -1 : (Y + X)
Modified: llvm/trunk/test/Transforms/InstCombine/saturating-add-sub.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/saturating-add-sub.ll?rev=354393&r1=354392&r2=354393&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/saturating-add-sub.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/saturating-add-sub.ll Tue Feb 19 14:14:21 2019
@@ -706,11 +706,10 @@ define <2 x i32> @uadd_sat_ugt_commute_a
define i32 @uadd_sat_commute_select(i32 %x, i32 %yp) {
; CHECK-LABEL: @uadd_sat_commute_select(
; CHECK-NEXT: [[Y:%.*]] = sdiv i32 [[YP:%.*]], 2442
-; CHECK-NEXT: [[NOTX:%.*]] = xor i32 [[X:%.*]], -1
-; CHECK-NEXT: [[A:%.*]] = add i32 [[Y]], [[X]]
-; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[Y]], [[NOTX]]
-; CHECK-NEXT: [[R:%.*]] = select i1 [[C]], i32 [[A]], i32 -1
-; CHECK-NEXT: ret i32 [[R]]
+; CHECK-NEXT: [[A:%.*]] = add i32 [[Y]], [[X:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i32 [[A]], [[Y]]
+; CHECK-NEXT: [[TMP2:%.*]] = select i1 [[TMP1]], i32 -1, i32 [[A]]
+; CHECK-NEXT: ret i32 [[TMP2]]
;
%y = sdiv i32 %yp, 2442 ; thwart complexity-based-canonicalization
%notx = xor i32 %x, -1
@@ -724,11 +723,10 @@ define i32 @uadd_sat_commute_select_comm
; CHECK-LABEL: @uadd_sat_commute_select_commute_add(
; CHECK-NEXT: [[X:%.*]] = urem i32 42, [[XP:%.*]]
; CHECK-NEXT: [[Y:%.*]] = sdiv i32 [[YP:%.*]], 2442
-; CHECK-NEXT: [[NOTX:%.*]] = xor i32 [[X]], -1
; CHECK-NEXT: [[A:%.*]] = add nsw i32 [[X]], [[Y]]
-; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[Y]], [[NOTX]]
-; CHECK-NEXT: [[R:%.*]] = select i1 [[C]], i32 [[A]], i32 -1
-; CHECK-NEXT: ret i32 [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i32 [[A]], [[Y]]
+; CHECK-NEXT: [[TMP2:%.*]] = select i1 [[TMP1]], i32 -1, i32 [[A]]
+; CHECK-NEXT: ret i32 [[TMP2]]
;
%x = urem i32 42, %xp ; thwart complexity-based-canonicalization
%y = sdiv i32 %yp, 2442 ; thwart complexity-based-canonicalization
@@ -741,11 +739,10 @@ define i32 @uadd_sat_commute_select_comm
define <2 x i32> @uadd_sat_commute_select_ugt(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @uadd_sat_commute_select_ugt(
-; CHECK-NEXT: [[NOTX:%.*]] = xor <2 x i32> [[X:%.*]], <i32 -1, i32 -1>
-; CHECK-NEXT: [[A:%.*]] = add <2 x i32> [[Y:%.*]], [[X]]
-; CHECK-NEXT: [[C:%.*]] = icmp ugt <2 x i32> [[NOTX]], [[Y]]
-; CHECK-NEXT: [[R:%.*]] = select <2 x i1> [[C]], <2 x i32> [[A]], <2 x i32> <i32 -1, i32 -1>
-; CHECK-NEXT: ret <2 x i32> [[R]]
+; CHECK-NEXT: [[A:%.*]] = add <2 x i32> [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <2 x i32> [[A]], [[Y]]
+; CHECK-NEXT: [[TMP2:%.*]] = select <2 x i1> [[TMP1]], <2 x i32> <i32 -1, i32 -1>, <2 x i32> [[A]]
+; CHECK-NEXT: ret <2 x i32> [[TMP2]]
;
%notx = xor <2 x i32> %x, <i32 -1, i32 -1>
%a = add <2 x i32> %y, %x
@@ -757,11 +754,10 @@ define <2 x i32> @uadd_sat_commute_selec
define i32 @uadd_sat_commute_select_ugt_commute_add(i32 %xp, i32 %y) {
; CHECK-LABEL: @uadd_sat_commute_select_ugt_commute_add(
; CHECK-NEXT: [[X:%.*]] = srem i32 42, [[XP:%.*]]
-; CHECK-NEXT: [[NOTX:%.*]] = xor i32 [[X]], -1
; CHECK-NEXT: [[A:%.*]] = add i32 [[X]], [[Y:%.*]]
-; CHECK-NEXT: [[C:%.*]] = icmp ugt i32 [[NOTX]], [[Y]]
-; CHECK-NEXT: [[R:%.*]] = select i1 [[C]], i32 [[A]], i32 -1
-; CHECK-NEXT: ret i32 [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i32 [[A]], [[Y]]
+; CHECK-NEXT: [[TMP2:%.*]] = select i1 [[TMP1]], i32 -1, i32 [[A]]
+; CHECK-NEXT: ret i32 [[TMP2]]
;
%x = srem i32 42, %xp ; thwart complexity-based-canonicalization
%notx = xor i32 %x, -1
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