[PatternMatch] Add support for capture-and-match (NFC) (#149825)

When using PatternMatch, there is a common problem where we want to both
match something against a pattern, but also capture the
value/instruction for various reasons (e.g. to access flags).

Currently the two ways to do that is to either capture using
m_Value/m_Instruction and do a separate match on the result, or to use
the somewhat awkward `m_CombineAnd(m_XYZ, m_Value(V))` pattern.

This PR introduces to add a variant of `m_Value`/`m_Instruction` which
does both a capture and a match. `m_Value(V, m_XYZ)` is basically
equivalent to `m_CombineAnd(m_XYZ, m_Value(V))`.

I've ported two InstCombine files to this pattern as a sample.

1 files changed, 7 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 7f605be..d934638 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1355,9 +1355,9 @@ Instruction *InstCombinerImpl::
   // right-shift of X and a "select".
   Value *X, *Select;
   Instruction *LowBitsToSkip, *Extract;
-  if (!match(&I, m_c_BinOp(m_TruncOrSelf(m_CombineAnd(
-                               m_LShr(m_Value(X), m_Instruction(LowBitsToSkip)),
-                               m_Instruction(Extract))),
+  if (!match(&I, m_c_BinOp(m_TruncOrSelf(m_Instruction(
+                               Extract, m_LShr(m_Value(X),
+                                               m_Instruction(LowBitsToSkip)))),
                            m_Value(Select))))
     return nullptr;
 
@@ -1763,13 +1763,12 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
     Constant *C;
     // (add X, (sext/zext (icmp eq X, C)))
     //    -> (select (icmp eq X, C), (add C, (sext/zext 1)), X)
-    auto CondMatcher = m_CombineAnd(
-        m_Value(Cond),
-        m_SpecificICmp(ICmpInst::ICMP_EQ, m_Deferred(A), m_ImmConstant(C)));
+    auto CondMatcher =
+        m_Value(Cond, m_SpecificICmp(ICmpInst::ICMP_EQ, m_Deferred(A),
+                                     m_ImmConstant(C)));
 
     if (match(&I,
-              m_c_Add(m_Value(A),
-                      m_CombineAnd(m_Value(Ext), m_ZExtOrSExt(CondMatcher)))) &&
+              m_c_Add(m_Value(A), m_Value(Ext, m_ZExtOrSExt(CondMatcher)))) &&
         Ext->hasOneUse()) {
       Value *Add = isa<ZExtInst>(Ext) ? InstCombiner::AddOne(C)
                                       : InstCombiner::SubOne(C);