Factor check for the assume intrinsic out of checks in computeKnownBitsFromAssume

We were matching against the assume intrinsic in every check.  Since we know that it must be an assume, this is just wasted work.  Somewhat surprisingly, matching an intrinsic id is actually relatively expensive.  It devolves to a string construction and comparison in Function::isIntrinsic.

I originally spotted this because it showed up in a performance profile of my compiler.  I've since discovered a separate issue which seems to be the actual root cause, but this is minor perf goodness regardless.

I'm likely to follow up with another change to factor out the comparison matching.  There's no need to match the compare instruction in every single one of the tests.

Differential Revision: http://reviews.llvm.org/D6312

llvm-svn: 222709

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index e9bbf83..ced5151 100644 (file)
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -491,7 +491,17 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
     if (Q.ExclInvs.count(I))
       continue;
 
-    if (match(I, m_Intrinsic<Intrinsic::assume>(m_Specific(V))) &&
+    // Warning: This loop can end up being somewhat performance sensetive.
+    // We're running this loop for once for each value queried resulting in a
+    // runtime of ~O(#assumes * #values).
+
+    assert(isa<IntrinsicInst>(I) &&
+           dyn_cast<IntrinsicInst>(I)->getIntrinsicID() == Intrinsic::assume &&
+           "must be an assume intrinsic");
+    
+    Value *Arg = I->getArgOperand(0);
+
+    if (Arg == V &&
         isValidAssumeForContext(I, Q, DL)) {
       assert(BitWidth == 1 && "assume operand is not i1?");
       KnownZero.clearAllBits();
@@ -507,16 +517,15 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
     CmpInst::Predicate Pred;
     ConstantInt *C;
     // assume(v = a)
-    if (match(I, m_Intrinsic<Intrinsic::assume>(
-                   m_c_ICmp(Pred, m_V, m_Value(A)))) &&
+    if (match(Arg, m_c_ICmp(Pred, m_V, m_Value(A))) &&
         Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
       KnownZero |= RHSKnownZero;
       KnownOne  |= RHSKnownOne;
     // assume(v & b = a)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_c_ICmp(Pred, m_c_And(m_V, m_Value(B)), m_Value(A)))) &&
+    } else if (match(Arg, m_c_ICmp(Pred, m_c_And(m_V, m_Value(B)),
+                                   m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
@@ -528,9 +537,8 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |= RHSKnownZero & MaskKnownOne;
       KnownOne  |= RHSKnownOne  & MaskKnownOne;
     // assume(~(v & b) = a)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_c_ICmp(Pred, m_Not(m_c_And(m_V, m_Value(B))),
-                                m_Value(A)))) &&
+    } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_c_And(m_V, m_Value(B))),
+                                   m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
@@ -542,8 +550,8 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |= RHSKnownOne  & MaskKnownOne;
       KnownOne  |= RHSKnownZero & MaskKnownOne;
     // assume(v | b = a)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_c_ICmp(Pred, m_c_Or(m_V, m_Value(B)), m_Value(A)))) &&
+    } else if (match(Arg, m_c_ICmp(Pred, m_c_Or(m_V, m_Value(B)),
+                                   m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
@@ -555,9 +563,8 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |= RHSKnownZero & BKnownZero;
       KnownOne  |= RHSKnownOne  & BKnownZero;
     // assume(~(v | b) = a)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_c_ICmp(Pred, m_Not(m_c_Or(m_V, m_Value(B))),
-                                m_Value(A)))) &&
+    } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_c_Or(m_V, m_Value(B))),
+                                   m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
@@ -569,8 +576,8 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |= RHSKnownOne  & BKnownZero;
       KnownOne  |= RHSKnownZero & BKnownZero;
     // assume(v ^ b = a)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_c_ICmp(Pred, m_c_Xor(m_V, m_Value(B)), m_Value(A)))) &&
+    } else if (match(Arg, m_c_ICmp(Pred, m_c_Xor(m_V, m_Value(B)),
+                                   m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
@@ -585,9 +592,8 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |= RHSKnownOne  & BKnownOne;
       KnownOne  |= RHSKnownZero & BKnownOne;
     // assume(~(v ^ b) = a)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_c_ICmp(Pred, m_Not(m_c_Xor(m_V, m_Value(B))),
-                                m_Value(A)))) &&
+    } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_c_Xor(m_V, m_Value(B))),
+                                   m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
@@ -602,9 +608,8 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |= RHSKnownZero & BKnownOne;
       KnownOne  |= RHSKnownOne  & BKnownOne;
     // assume(v << c = a)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_c_ICmp(Pred, m_Shl(m_V, m_ConstantInt(C)),
-                                      m_Value(A)))) &&
+    } else if (match(Arg, m_c_ICmp(Pred, m_Shl(m_V, m_ConstantInt(C)),
+                                   m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
@@ -613,9 +618,8 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |= RHSKnownZero.lshr(C->getZExtValue());
       KnownOne  |= RHSKnownOne.lshr(C->getZExtValue());
     // assume(~(v << c) = a)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_c_ICmp(Pred, m_Not(m_Shl(m_V, m_ConstantInt(C))),
-                                      m_Value(A)))) &&
+    } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_Shl(m_V, m_ConstantInt(C))),
+                                   m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
@@ -624,11 +628,11 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |= RHSKnownOne.lshr(C->getZExtValue());
       KnownOne  |= RHSKnownZero.lshr(C->getZExtValue());
     // assume(v >> c = a)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_c_ICmp(Pred, m_CombineOr(m_LShr(m_V, m_ConstantInt(C)),
+    } else if (match(Arg,
+                     m_c_ICmp(Pred, m_CombineOr(m_LShr(m_V, m_ConstantInt(C)),
                                                   m_AShr(m_V,
                                                          m_ConstantInt(C))),
-                                     m_Value(A)))) &&
+                                     m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
@@ -637,11 +641,10 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |= RHSKnownZero << C->getZExtValue();
       KnownOne  |= RHSKnownOne  << C->getZExtValue();
     // assume(~(v >> c) = a)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_c_ICmp(Pred, m_Not(m_CombineOr(
+    } else if (match(Arg, m_c_ICmp(Pred, m_Not(m_CombineOr(
                                               m_LShr(m_V, m_ConstantInt(C)),
                                               m_AShr(m_V, m_ConstantInt(C)))),
-                                     m_Value(A)))) &&
+                                   m_Value(A))) &&
                Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
       computeKnownBits(A, RHSKnownZero, RHSKnownOne, DL, Depth+1, Query(Q, I));
@@ -650,8 +653,7 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |= RHSKnownOne  << C->getZExtValue();
       KnownOne  |= RHSKnownZero << C->getZExtValue();
     // assume(v >=_s c) where c is non-negative
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_ICmp(Pred, m_V, m_Value(A)))) &&
+    } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
                Pred == ICmpInst::ICMP_SGE &&
                isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
@@ -662,8 +664,7 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
         KnownZero |= APInt::getSignBit(BitWidth);
       }
     // assume(v >_s c) where c is at least -1.
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_ICmp(Pred, m_V, m_Value(A)))) &&
+    } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
                Pred == ICmpInst::ICMP_SGT &&
                isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
@@ -674,8 +675,7 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
         KnownZero |= APInt::getSignBit(BitWidth);
       }
     // assume(v <=_s c) where c is negative
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_ICmp(Pred, m_V, m_Value(A)))) &&
+    } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
                Pred == ICmpInst::ICMP_SLE &&
                isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
@@ -686,8 +686,7 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
         KnownOne |= APInt::getSignBit(BitWidth);
       }
     // assume(v <_s c) where c is non-positive
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_ICmp(Pred, m_V, m_Value(A)))) &&
+    } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
                Pred == ICmpInst::ICMP_SLT &&
                isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
@@ -698,8 +697,7 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
         KnownOne |= APInt::getSignBit(BitWidth);
       }
     // assume(v <=_u c)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_ICmp(Pred, m_V, m_Value(A)))) &&
+    } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
                Pred == ICmpInst::ICMP_ULE &&
                isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
@@ -709,8 +707,7 @@ static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
       KnownZero |=
         APInt::getHighBitsSet(BitWidth, RHSKnownZero.countLeadingOnes());
     // assume(v <_u c)
-    } else if (match(I, m_Intrinsic<Intrinsic::assume>(
-                       m_ICmp(Pred, m_V, m_Value(A)))) &&
+    } else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
                Pred == ICmpInst::ICMP_ULT &&
                isValidAssumeForContext(I, Q, DL)) {
       APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);