[ValueTracking] Remove SPF support from computeKnownBitsFromOperator
#76630
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@llvm/pr-subscribers-llvm-analysis @llvm/pr-subscribers-llvm-transforms Author: Yingwei Zheng (dtcxzyw) ChangesThis patch removes redundant SPF support (5350e1b) from Compile-time improvement:
Full diff: https://github.com/llvm/llvm-project/pull/76630.diff 4 Files Affected:
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index cac2602d455f9d..16d78c1ded6d7a 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -983,45 +983,11 @@ static void computeKnownBitsFromOperator(const Operator *I,
break;
}
case Instruction::Select: {
- const Value *LHS = nullptr, *RHS = nullptr;
- SelectPatternFlavor SPF = matchSelectPattern(I, LHS, RHS).Flavor;
- if (SelectPatternResult::isMinOrMax(SPF)) {
- computeKnownBits(RHS, Known, Depth + 1, Q);
- computeKnownBits(LHS, Known2, Depth + 1, Q);
- switch (SPF) {
- default:
- llvm_unreachable("Unhandled select pattern flavor!");
- case SPF_SMAX:
- Known = KnownBits::smax(Known, Known2);
- break;
- case SPF_SMIN:
- Known = KnownBits::smin(Known, Known2);
- break;
- case SPF_UMAX:
- Known = KnownBits::umax(Known, Known2);
- break;
- case SPF_UMIN:
- Known = KnownBits::umin(Known, Known2);
- break;
- }
- break;
- }
-
computeKnownBits(I->getOperand(2), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
// Only known if known in both the LHS and RHS.
Known = Known.intersectWith(Known2);
-
- if (SPF == SPF_ABS) {
- // RHS from matchSelectPattern returns the negation part of abs pattern.
- // If the negate has an NSW flag we can assume the sign bit of the result
- // will be 0 because that makes abs(INT_MIN) undefined.
- if (match(RHS, m_Neg(m_Specific(LHS))) &&
- Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(RHS)))
- Known.Zero.setSignBit();
- }
-
break;
}
case Instruction::FPTrunc:
diff --git a/llvm/test/Analysis/ScalarEvolution/max-expr-cache.ll b/llvm/test/Analysis/ScalarEvolution/max-expr-cache.ll
index d401ff31035e8f..c2d90537506938 100644
--- a/llvm/test/Analysis/ScalarEvolution/max-expr-cache.ll
+++ b/llvm/test/Analysis/ScalarEvolution/max-expr-cache.ll
@@ -229,21 +229,21 @@ define void @umax(i32 %tmp3) {
; CHECK-NEXT: %tmp48 = select i1 %tmp47, i32 %tmp44, i32 %tmp46
; CHECK-NEXT: --> ((7 + (256 umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umax (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>)) U: [7,264) S: [7,264) Exits: <<Unknown>> LoopDispositions: { %bb4: Computable, %bb53: Invariant }
; CHECK-NEXT: %tmp49 = ashr i32 %tmp48, 3
-; CHECK-NEXT: --> %tmp49 U: [0,128) S: [0,128) Exits: <<Unknown>> LoopDispositions: { %bb4: Variant, %bb53: Invariant }
+; CHECK-NEXT: --> %tmp49 U: [-268435456,268435456) S: [-268435456,268435456) Exits: <<Unknown>> LoopDispositions: { %bb4: Variant, %bb53: Invariant }
; CHECK-NEXT: %tmp51 = select i1 %tmp50, i32 %tmp49, i32 0
-; CHECK-NEXT: --> %tmp49 U: [0,128) S: [0,128) Exits: <<Unknown>> LoopDispositions: { %bb4: Variant, %bb53: Invariant }
+; CHECK-NEXT: --> %tmp49 U: [-268435456,268435456) S: [-268435456,268435456) Exits: <<Unknown>> LoopDispositions: { %bb4: Variant, %bb53: Invariant }
; CHECK-NEXT: %tmp52 = zext i32 %tmp51 to i64
-; CHECK-NEXT: --> (zext i32 %tmp49 to i64) U: [0,128) S: [0,128) Exits: <<Unknown>> LoopDispositions: { %bb4: Variant, %bb53: Invariant }
+; CHECK-NEXT: --> (zext i32 %tmp49 to i64) U: [0,4294967296) S: [0,4294967296) Exits: <<Unknown>> LoopDispositions: { %bb4: Variant, %bb53: Invariant }
; CHECK-NEXT: %tmp54 = phi i64 [ undef, %bb4 ], [ %tmp59, %bb53 ]
; CHECK-NEXT: --> {undef,+,1}<nsw><%bb53> U: full-set S: full-set Exits: (-1 + (zext i32 %tmp49 to i64))<nsw> LoopDispositions: { %bb53: Computable, %bb4: Variant }
; CHECK-NEXT: %tmp55 = trunc i64 %tmp54 to i32
; CHECK-NEXT: --> {(trunc i64 undef to i32),+,1}<%bb53> U: full-set S: full-set Exits: (-1 + %tmp49)<nsw> LoopDispositions: { %bb53: Computable, %bb4: Variant }
; CHECK-NEXT: %tmp56 = shl nsw i32 %tmp55, 3
-; CHECK-NEXT: --> {(8 * (trunc i64 undef to i32)),+,8}<%bb53> U: [0,-7) S: [-2147483648,2147483641) Exits: (-8 + (8 * %tmp49)<nuw><nsw>)<nsw> LoopDispositions: { %bb53: Computable, %bb4: Variant }
+; CHECK-NEXT: --> {(8 * (trunc i64 undef to i32)),+,8}<%bb53> U: [0,-7) S: [-2147483648,2147483641) Exits: (-8 + (8 * %tmp49)<nsw>) LoopDispositions: { %bb53: Computable, %bb4: Variant }
; CHECK-NEXT: %tmp57 = sext i32 %tmp56 to i64
-; CHECK-NEXT: --> (sext i32 {(8 * (trunc i64 undef to i32)),+,8}<%bb53> to i64) U: [0,-7) S: [-2147483648,2147483641) Exits: (-8 + (8 * (zext i32 %tmp49 to i64))<nuw><nsw>)<nsw> LoopDispositions: { %bb53: Computable, %bb4: Variant }
+; CHECK-NEXT: --> (sext i32 {(8 * (trunc i64 undef to i32)),+,8}<%bb53> to i64) U: [0,-7) S: [-2147483648,2147483641) Exits: (sext i32 (-8 + (8 * %tmp49)<nsw>) to i64) LoopDispositions: { %bb53: Computable, %bb4: Variant }
; CHECK-NEXT: %tmp58 = getelementptr inbounds i8, ptr null, i64 %tmp57
-; CHECK-NEXT: --> ((sext i32 {(8 * (trunc i64 undef to i32)),+,8}<%bb53> to i64) + null) U: [0,-7) S: [-2147483648,2147483641) Exits: (-8 + (8 * (zext i32 %tmp49 to i64))<nuw><nsw> + null) LoopDispositions: { %bb53: Computable, %bb4: Variant }
+; CHECK-NEXT: --> ((sext i32 {(8 * (trunc i64 undef to i32)),+,8}<%bb53> to i64) + null) U: [0,-7) S: [-2147483648,2147483641) Exits: ((sext i32 (-8 + (8 * %tmp49)<nsw>) to i64) + null) LoopDispositions: { %bb53: Computable, %bb4: Variant }
; CHECK-NEXT: %tmp59 = add nsw i64 %tmp54, 1
; CHECK-NEXT: --> {(1 + undef),+,1}<nsw><%bb53> U: full-set S: full-set Exits: (zext i32 %tmp49 to i64) LoopDispositions: { %bb53: Computable, %bb4: Variant }
; CHECK-NEXT: %tmp62 = add nuw nsw i64 %tmp5, 1
diff --git a/llvm/test/Transforms/LoopIdiom/ARM/ctlz.ll b/llvm/test/Transforms/LoopIdiom/ARM/ctlz.ll
index ec9271a683f47d..c80c94c90534dd 100644
--- a/llvm/test/Transforms/LoopIdiom/ARM/ctlz.ll
+++ b/llvm/test/Transforms/LoopIdiom/ARM/ctlz.ll
@@ -31,9 +31,7 @@
; Function Attrs: norecurse nounwind uwtable
define i32 @ctlz_and_other(i32 %n, ptr nocapture %a) {
entry:
- %c = icmp sgt i32 %n, 0
- %negn = sub nsw i32 0, %n
- %abs_n = select i1 %c, i32 %n, i32 %negn
+ %abs_n = call i32 @llvm.abs.i32(i32 %n, i1 true)
%shr8 = lshr i32 %abs_n, 1
%tobool9 = icmp eq i32 %shr8, 0
br i1 %tobool9, label %while.end, label %while.body.preheader
@@ -90,9 +88,7 @@ while.end: ; preds = %while.end.loopexit,
; Function Attrs: norecurse nounwind readnone uwtable
define i32 @ctlz_zero_check(i32 %n) {
entry:
- %c = icmp sgt i32 %n, 0
- %negn = sub nsw i32 0, %n
- %abs_n = select i1 %c, i32 %n, i32 %negn
+ %abs_n = call i32 @llvm.abs.i32(i32 %n, i1 true)
%tobool4 = icmp eq i32 %abs_n, 0
br i1 %tobool4, label %while.end, label %while.body.preheader
@@ -140,9 +136,7 @@ while.end: ; preds = %while.end.loopexit,
; Function Attrs: norecurse nounwind readnone uwtable
define i32 @ctlz(i32 %n) {
entry:
- %c = icmp sgt i32 %n, 0
- %negn = sub nsw i32 0, %n
- %abs_n = select i1 %c, i32 %n, i32 %negn
+ %abs_n = call i32 @llvm.abs.i32(i32 %n, i1 true)
br label %while.cond
while.cond: ; preds = %while.cond, %entry
@@ -183,9 +177,7 @@ while.end: ; preds = %while.cond
; Function Attrs: norecurse nounwind readnone uwtable
define i32 @ctlz_add(i32 %n, i32 %i0) {
entry:
- %c = icmp sgt i32 %n, 0
- %negn = sub nsw i32 0, %n
- %abs_n = select i1 %c, i32 %n, i32 %negn
+ %abs_n = call i32 @llvm.abs.i32(i32 %n, i1 true)
br label %while.cond
while.cond: ; preds = %while.cond, %entry
@@ -227,10 +219,8 @@ while.end: ; preds = %while.cond
; Function Attrs: norecurse nounwind readnone uwtable
define i32 @ctlz_sext(i16 %in) {
entry:
- %n = sext i16 %in to i32
- %c = icmp sgt i16 %in, 0
- %negn = sub nsw i32 0, %n
- %abs_n = select i1 %c, i32 %n, i32 %negn
+ %abs = call i16 @llvm.abs.i16(i16 %in, i1 false)
+ %abs_n = zext i16 %abs to i32
br label %while.cond
while.cond: ; preds = %while.cond, %entry
@@ -244,3 +234,6 @@ while.cond: ; preds = %while.cond, %entry
while.end: ; preds = %while.cond
ret i32 %i.0
}
+
+declare i32 @llvm.abs.i32(i32, i1)
+declare i16 @llvm.abs.i16(i16, i1)
diff --git a/llvm/test/Transforms/LoopIdiom/X86/ctlz.ll b/llvm/test/Transforms/LoopIdiom/X86/ctlz.ll
index 8ea8ba8f346399..1b57fcc3966763 100644
--- a/llvm/test/Transforms/LoopIdiom/X86/ctlz.ll
+++ b/llvm/test/Transforms/LoopIdiom/X86/ctlz.ll
@@ -20,9 +20,7 @@
define i32 @ctlz_and_other(i32 %n, ptr nocapture %a) {
; ALL-LABEL: @ctlz_and_other(
; ALL-NEXT: entry:
-; ALL-NEXT: [[C:%.*]] = icmp sgt i32 [[N:%.*]], 0
-; ALL-NEXT: [[NEGN:%.*]] = sub nsw i32 0, [[N]]
-; ALL-NEXT: [[ABS_N:%.*]] = select i1 [[C]], i32 [[N]], i32 [[NEGN]]
+; ALL-NEXT: [[ABS_N:%.*]] = call i32 @llvm.abs.i32(i32 [[N:%.*]], i1 true)
; ALL-NEXT: [[SHR8:%.*]] = lshr i32 [[ABS_N]], 1
; ALL-NEXT: [[TOBOOL9:%.*]] = icmp eq i32 [[SHR8]], 0
; ALL-NEXT: br i1 [[TOBOOL9]], label [[WHILE_END:%.*]], label [[WHILE_BODY_PREHEADER:%.*]]
@@ -56,9 +54,7 @@ define i32 @ctlz_and_other(i32 %n, ptr nocapture %a) {
; ALL-NEXT: ret i32 [[I_0_LCSSA]]
;
entry:
- %c = icmp sgt i32 %n, 0
- %negn = sub nsw i32 0, %n
- %abs_n = select i1 %c, i32 %n, i32 %negn
+ %abs_n = call i32 @llvm.abs.i32(i32 %n, i1 true)
%shr8 = lshr i32 %abs_n, 1
%tobool9 = icmp eq i32 %shr8, 0
br i1 %tobool9, label %while.end, label %while.body.preheader
@@ -108,9 +104,7 @@ while.end: ; preds = %while.end.loopexit,
define i32 @ctlz_zero_check(i32 %n) {
; ALL-LABEL: @ctlz_zero_check(
; ALL-NEXT: entry:
-; ALL-NEXT: [[C:%.*]] = icmp sgt i32 [[N:%.*]], 0
-; ALL-NEXT: [[NEGN:%.*]] = sub nsw i32 0, [[N]]
-; ALL-NEXT: [[ABS_N:%.*]] = select i1 [[C]], i32 [[N]], i32 [[NEGN]]
+; ALL-NEXT: [[ABS_N:%.*]] = call i32 @llvm.abs.i32(i32 [[N:%.*]], i1 true)
; ALL-NEXT: [[TOBOOL4:%.*]] = icmp eq i32 [[ABS_N]], 0
; ALL-NEXT: br i1 [[TOBOOL4]], label [[WHILE_END:%.*]], label [[WHILE_BODY_PREHEADER:%.*]]
; ALL: while.body.preheader:
@@ -134,9 +128,7 @@ define i32 @ctlz_zero_check(i32 %n) {
; ALL-NEXT: ret i32 [[I_0_LCSSA]]
;
entry:
- %c = icmp sgt i32 %n, 0
- %negn = sub nsw i32 0, %n
- %abs_n = select i1 %c, i32 %n, i32 %negn
+ %abs_n = call i32 @llvm.abs.i32(i32 %n, i1 true)
%tobool4 = icmp eq i32 %abs_n, 0
br i1 %tobool4, label %while.end, label %while.body.preheader
@@ -238,9 +230,7 @@ while.end: ; preds = %while.end.loopexit,
define i32 @ctlz(i32 %n) {
; ALL-LABEL: @ctlz(
; ALL-NEXT: entry:
-; ALL-NEXT: [[C:%.*]] = icmp sgt i32 [[N:%.*]], 0
-; ALL-NEXT: [[NEGN:%.*]] = sub nsw i32 0, [[N]]
-; ALL-NEXT: [[ABS_N:%.*]] = select i1 [[C]], i32 [[N]], i32 [[NEGN]]
+; ALL-NEXT: [[ABS_N:%.*]] = call i32 @llvm.abs.i32(i32 [[N:%.*]], i1 true)
; ALL-NEXT: [[TMP0:%.*]] = ashr i32 [[ABS_N]], 1
; ALL-NEXT: [[TMP1:%.*]] = call i32 @llvm.ctlz.i32(i32 [[TMP0]], i1 false)
; ALL-NEXT: [[TMP2:%.*]] = sub i32 32, [[TMP1]]
@@ -260,9 +250,7 @@ define i32 @ctlz(i32 %n) {
; ALL-NEXT: ret i32 [[I_0_LCSSA]]
;
entry:
- %c = icmp sgt i32 %n, 0
- %negn = sub nsw i32 0, %n
- %abs_n = select i1 %c, i32 %n, i32 %negn
+ %abs_n = call i32 @llvm.abs.i32(i32 %n, i1 true)
br label %while.cond
while.cond: ; preds = %while.cond, %entry
@@ -343,9 +331,7 @@ while.end: ; preds = %while.cond
define i32 @ctlz_add(i32 %n, i32 %i0) {
; ALL-LABEL: @ctlz_add(
; ALL-NEXT: entry:
-; ALL-NEXT: [[C:%.*]] = icmp sgt i32 [[N:%.*]], 0
-; ALL-NEXT: [[NEGN:%.*]] = sub nsw i32 0, [[N]]
-; ALL-NEXT: [[ABS_N:%.*]] = select i1 [[C]], i32 [[N]], i32 [[NEGN]]
+; ALL-NEXT: [[ABS_N:%.*]] = call i32 @llvm.abs.i32(i32 [[N:%.*]], i1 true)
; ALL-NEXT: [[TMP0:%.*]] = ashr i32 [[ABS_N]], 1
; ALL-NEXT: [[TMP1:%.*]] = call i32 @llvm.ctlz.i32(i32 [[TMP0]], i1 false)
; ALL-NEXT: [[TMP2:%.*]] = sub i32 32, [[TMP1]]
@@ -366,9 +352,7 @@ define i32 @ctlz_add(i32 %n, i32 %i0) {
; ALL-NEXT: ret i32 [[I_0_LCSSA]]
;
entry:
- %c = icmp sgt i32 %n, 0
- %negn = sub nsw i32 0, %n
- %abs_n = select i1 %c, i32 %n, i32 %negn
+ %abs_n = call i32 @llvm.abs.i32(i32 %n, i1 true)
br label %while.cond
while.cond: ; preds = %while.cond, %entry
@@ -452,10 +436,8 @@ while.end: ; preds = %while.cond
define i32 @ctlz_sext(i16 %in) {
; ALL-LABEL: @ctlz_sext(
; ALL-NEXT: entry:
-; ALL-NEXT: [[N:%.*]] = sext i16 [[IN:%.*]] to i32
-; ALL-NEXT: [[C:%.*]] = icmp sgt i16 [[IN]], 0
-; ALL-NEXT: [[NEGN:%.*]] = sub nsw i32 0, [[N]]
-; ALL-NEXT: [[ABS_N:%.*]] = select i1 [[C]], i32 [[N]], i32 [[NEGN]]
+; ALL-NEXT: [[ABS:%.*]] = call i16 @llvm.abs.i16(i16 [[IN:%.*]], i1 false)
+; ALL-NEXT: [[ABS_N:%.*]] = zext i16 [[ABS]] to i32
; ALL-NEXT: [[TMP0:%.*]] = ashr i32 [[ABS_N]], 1
; ALL-NEXT: [[TMP1:%.*]] = call i32 @llvm.ctlz.i32(i32 [[TMP0]], i1 false)
; ALL-NEXT: [[TMP2:%.*]] = sub i32 32, [[TMP1]]
@@ -475,10 +457,8 @@ define i32 @ctlz_sext(i16 %in) {
; ALL-NEXT: ret i32 [[I_0_LCSSA]]
;
entry:
- %n = sext i16 %in to i32
- %c = icmp sgt i16 %in, 0
- %negn = sub nsw i32 0, %n
- %abs_n = select i1 %c, i32 %n, i32 %negn
+ %abs = call i16 @llvm.abs.i16(i16 %in, i1 false)
+ %abs_n = zext i16 %abs to i32
br label %while.cond
while.cond: ; preds = %while.cond, %entry
@@ -753,3 +733,6 @@ while.cond: ; preds = %while.cond, %entry
while.end: ; preds = %while.cond
ret i32 %i.0
}
+
+declare i32 @llvm.abs.i32(i32, i1)
+declare i16 @llvm.abs.i16(i16, i1)
|
dtcxzyw
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Dec 30, 2023
nikic
approved these changes
Dec 30, 2023
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This patch removes redundant SPF support (5350e1b) from
computeKnownBitsFromOperatoras we always canonicalize a SPF into an intrinsic call.Compile-time improvement: http://llvm-compile-time-tracker.com/compare.php?from=3dc0638cfc19e140daff7bf1281648daca8212fa&to=8771ef0749fb2ba4304dc68d418c88ec5769346f&stat=instructions:u