[llvm] r354276 - [InstCombine] reduce even more unsigned saturated add with 'not' op
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Mon Feb 18 07:21:40 PST 2019
Author: spatel
Date: Mon Feb 18 07:21:39 2019
New Revision: 354276
URL: http://llvm.org/viewvc/llvm-project?rev=354276&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=354276&r1=354275&r2=354276&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp Mon Feb 18 07:21:39 2019
@@ -680,25 +680,46 @@ static Value *canonicalizeSaturatedAdd(I
if (!Cmp->hasOneUse())
return nullptr;
- // Canonicalize to 'ULT' to simplify matching below.
Value *Cmp0 = Cmp->getOperand(0);
Value *Cmp1 = Cmp->getOperand(1);
+
+ // Match unsigned saturated add with constant.
+ Value *X;
+ const APInt *C, *CmpC;
+ if (match(TVal, m_Add(m_Value(X), m_APInt(C))) && X == Cmp0 &&
+ match(Cmp1, m_APInt(CmpC)) && *CmpC == ~*C) {
+ // Commute compare predicate and select operands. The backend is expecting
+ // this form (-1 is true value). If this changes, the backend must be
+ // updated too:
+ // (X u< ~C) ? (X + C) : -1 --> (X u> ~C) ? -1 : (X + C)
+ Value *NewCmp = Builder.CreateICmp(ICmpInst::ICMP_UGT, X, Cmp1);
+ return Builder.CreateSelect(NewCmp, FVal, TVal);
+ }
+
+ // 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'.
ICmpInst::Predicate Pred = Cmp->getPredicate();
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 *X, *Y;
- if (match(TVal, m_AllOnes()) && match(Cmp0, m_Not(m_Value(X))) &&
+ Value *Y;
+ 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)
@@ -706,16 +727,6 @@ static Value *canonicalizeSaturatedAdd(I
return Builder.CreateSelect(NewCmp, TVal, FVal);
}
- // Match unsigned saturated add with constant.
- const APInt *C, *CmpC;
- if (match(TVal, m_Add(m_Value(X), m_APInt(C))) && X == Cmp0 &&
- match(FVal, m_AllOnes()) && match(Cmp1, m_APInt(CmpC)) && *CmpC == ~*C) {
- // Commute compare predicate and select operands:
- // (X u< ~C) ? (X + C) : -1 --> (X u> ~C) ? -1 : (X + C)
- Value *NewCmp = Builder.CreateICmp(ICmpInst::ICMP_UGT, X, Cmp1);
- return Builder.CreateSelect(NewCmp, FVal, TVal);
- }
-
return nullptr;
}
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=354276&r1=354275&r2=354276&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/saturating-add-sub.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/saturating-add-sub.ll Mon Feb 18 07:21:39 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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