removed match and moved into selfmultiply condition, simplified condition to drop ternary and moved test to llvm/test/Transforms/InstCombine since wasn't folded with instsimplifiy

Author: Aethezz

llvm/lib/Analysis/ValueTracking.cpp

@@ -409,10 +409,24 @@ static void computeKnownBitsMul(const Value *Op0, const Value *Op1, bool NSW,
   }
 
   bool SelfMultiply = Op0 == Op1;
-  if (SelfMultiply)
+  if (SelfMultiply) {
     SelfMultiply &=
         isGuaranteedNotToBeUndef(Op0, Q.AC, Q.CxtI, Q.DT, Depth + 1);
-  Known = KnownBits::mul(Known, Known2, SelfMultiply);
+
+    Known = KnownBits::mul(Known, Known2, SelfMultiply);
+
+    unsigned SignBits = ComputeNumSignBits(Op0, DemandedElts, Q, Depth + 1);
+    unsigned TyBits = Op0->getType()->getScalarSizeInBits();
+    unsigned OutValidBits = 2 * (TyBits - SignBits + 1);
+
+    if (OutValidBits < TyBits) {
+      APInt KnownZeroMask =
+          APInt::getHighBitsSet(TyBits, TyBits - OutValidBits + 1);
+      Known.Zero |= KnownZeroMask;
+    }
+  } else {
+    Known = KnownBits::mul(Known, Known2, SelfMultiply);
+  }
 
   // Only make use of no-wrap flags if we failed to compute the sign bit
   // directly.  This matters if the multiplication always overflows, in
@@ -423,22 +437,6 @@ static void computeKnownBitsMul(const Value *Op0, const Value *Op1, bool NSW,
     Known.makeNonNegative();
   else if (isKnownNegative && !Known.isNonNegative())
     Known.makeNegative();
-
-  // Check if both operands are the same sign-extension of a single value.
-  const Value *A = nullptr;
-  if (match(Op0, m_SExt(m_Value(A))) && match(Op1, m_SExt(m_Specific(A)))) {
-    unsigned SignBits = ComputeNumSignBits(Op0, DemandedElts, Q, Depth + 1);
-    unsigned TyBits = Op0->getType()->getScalarSizeInBits();
-    // The output of the Mul can be at most twice the valid bits
-    unsigned OutValidBits = 2 * (TyBits - SignBits + 1);
-    unsigned OutSignBits =
-        OutValidBits > TyBits ? 1 : TyBits - OutValidBits + 1;
-
-    if (OutSignBits > 1) {
-      APInt KnownZeroMask = APInt::getHighBitsSet(TyBits, OutSignBits);
-      Known.Zero |= KnownZeroMask;
-    }
-  }
 }
 
 void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,

llvm/test/Analysis/ValueTracking/known-bits.ll

@@ -49,36 +49,3 @@ define i1 @vec_reverse_known_bits_demanded_fail(<4 x i8> %xx) {
   %r = icmp slt i8 %ele, 0
   ret i1 %r
 }
-
-; Test known bits for (sext i8 x) * (sext i8 x)
-; RUN: opt -passes=instcombine < %s -S | FileCheck %s --check-prefix=SEXT_SQUARE
-
-define i1 @sext_square_bit31(i8 %x) {
-; SEXT_SQUARE-LABEL: @sext_square_bit31(
-; SEXT_SQUARE-NEXT:    ret i1 false
-  %sx = sext i8 %x to i32
-  %mul = mul nsw i32 %sx, %sx
-  %and = and i32 %mul, 2147483648 ; 1 << 31
-  %cmp = icmp ne i32 %and, 0
-  ret i1 %cmp
-}
-
-define i1 @sext_square_bit30(i8 %x) {
-; SEXT_SQUARE-LABEL: @sext_square_bit30(
-; SEXT_SQUARE-NEXT:    ret i1 false
-  %sx = sext i8 %x to i32
-  %mul = mul nsw i32 %sx, %sx
-  %and = and i32 %mul, 1073741824 ; 1 << 30
-  %cmp = icmp ne i32 %and, 0
-  ret i1 %cmp
-}
-
-define i1 @sext_square_bit14(i8 %x) {
-; SEXT_SQUARE-LABEL: @sext_square_bit14(
-; SEXT_SQUARE-NOT: ret i1 false
-  %sx = sext i8 %x to i32
-  %mul = mul nsw i32 %sx, %sx
-  %and = and i32 %mul, 16384 ; 1 << 14
-  %cmp = icmp ne i32 %and, 0
-  ret i1 %cmp
-}

llvm/test/Transforms/InstCombine/sext.ll

@@ -423,3 +423,35 @@ define i64 @smear_set_bit_different_dest_type_wider_dst(i32 %x) {
   %s = sext i8 %a to i64
   ret i64 %s
 }
+
+; Test known bits for (sext i8 x) * (sext i8 x)
+
+define i1 @sext_square_bit30(i8 %x) {
+; CHECK-LABEL: @sext_square_bit30(
+; CHECK:  ret i1 false
+  %sx = sext i8 %x to i32
+  %mul = mul nsw i32 %sx, %sx
+  %and = and i32 %mul, 1073741824 ; 1 << 30
+  %cmp = icmp ne i32 %and, 0
+  ret i1 %cmp
+}
+
+define i1 @sext_square_bit15(i8 %x) {
+; CHECK-LABEL: @sext_square_bit15(
+; CHECK:  ret i1 false
+  %sx = sext i8 %x to i32
+  %mul = mul nsw i32 %sx, %sx
+  %and = and i32 %mul, 32768 ; 1 << 15
+  %cmp = icmp ne i32 %and, 0
+  ret i1 %cmp
+}
+
+define i1 @sext_square_bit14(i8 %x) {
+; CHECK-LABEL: @sext_square_bit14(
+; CHECK-NOT: ret i1 false
+  %sx = sext i8 %x to i32
+  %mul = mul nsw i32 %sx, %sx
+  %and = and i32 %mul, 16384 ; 1 << 14
+  %cmp = icmp ne i32 %and, 0
+  ret i1 %cmp
+}