Enable conditional compare chaining for AMD64.

Author: anthonycanino

src/coreclr/jit/codegen.h

@@ -969,7 +969,7 @@ class CodeGen final : public CodeGenInterface
     void genIntToFloatCast(GenTree* treeNode);
     void genCkfinite(GenTree* treeNode);
     void genCodeForCompare(GenTreeOp* tree);
-#ifdef TARGET_ARM64
+#if defined(TARGET_ARM64) || defined(TARGET_AMD64)
     void genCodeForCCMP(GenTreeCCMP* ccmp);
 #endif
     void genCodeForSelect(GenTreeOp* select);
@@ -1708,6 +1708,8 @@ class CodeGen final : public CodeGenInterface
     static insOpts ShiftOpToInsOpts(genTreeOps op);
 #elif defined(TARGET_XARCH)
     static instruction JumpKindToCmov(emitJumpKind condition);
+    static instruction JumpKindToCcmp(emitJumpKind condition);
+    static insOpts     OptsFromCFlags(insCflags flags);
 #endif
 
 #if !defined(TARGET_LOONGARCH64) && !defined(TARGET_RISCV64)

src/coreclr/jit/codegenxarch.cpp

@@ -1572,6 +1572,46 @@ instruction CodeGen::JumpKindToCmov(emitJumpKind condition)
     return s_table[condition];
 }
 
+//------------------------------------------------------------------------
+// JumpKindToCcmp:
+//   Convert an emitJumpKind to the corresponding ccmp instruction.
+//
+// Arguments:
+//    condition - the condition
+//
+// Returns:
+//    A ccmp instruction.
+//
+instruction CodeGen::JumpKindToCcmp(emitJumpKind condition)
+{
+    static constexpr instruction s_table[EJ_COUNT] = {
+        INS_none,  INS_none,  INS_ccmpo,  INS_ccmpno, INS_ccmpb, INS_ccmpae, INS_ccmpe,  INS_ccmpne, INS_ccmpbe,
+        INS_ccmpa, INS_ccmps, INS_ccmpns, INS_none,   INS_none,  INS_ccmpl,  INS_ccmpge, INS_ccmple, INS_ccmpg,
+    };
+
+    static_assert_no_msg(s_table[EJ_NONE] == INS_none);
+    static_assert_no_msg(s_table[EJ_jmp] == INS_none);
+    static_assert_no_msg(s_table[EJ_jo] == INS_ccmpo);
+    static_assert_no_msg(s_table[EJ_jno] == INS_ccmpno);
+    static_assert_no_msg(s_table[EJ_jb] == INS_ccmpb);
+    static_assert_no_msg(s_table[EJ_jae] == INS_ccmpae);
+    static_assert_no_msg(s_table[EJ_je] == INS_ccmpe);
+    static_assert_no_msg(s_table[EJ_jne] == INS_ccmpne);
+    static_assert_no_msg(s_table[EJ_jbe] == INS_ccmpbe);
+    static_assert_no_msg(s_table[EJ_ja] == INS_ccmpa);
+    static_assert_no_msg(s_table[EJ_js] == INS_ccmps);
+    static_assert_no_msg(s_table[EJ_jns] == INS_ccmpns);
+    static_assert_no_msg(s_table[EJ_jp] == INS_none);
+    static_assert_no_msg(s_table[EJ_jnp] == INS_none);
+    static_assert_no_msg(s_table[EJ_jl] == INS_ccmpl);
+    static_assert_no_msg(s_table[EJ_jge] == INS_ccmpge);
+    static_assert_no_msg(s_table[EJ_jle] == INS_ccmple);
+    static_assert_no_msg(s_table[EJ_jg] == INS_ccmpg);
+
+    assert((condition >= EJ_NONE) && (condition < EJ_COUNT));
+    return s_table[condition];
+}
+
 //------------------------------------------------------------------------
 // genCodeForCompare: Produce code for a GT_SELECT/GT_SELECTCC node.
 //
@@ -2260,6 +2300,12 @@ void CodeGen::genCodeForTreeNode(GenTree* treeNode)
             // Do nothing; these nodes are simply markers for debug info.
             break;
 
+#if defined(TARGET_AMD64)
+        case GT_CCMP:
+            genCodeForCCMP(treeNode->AsCCMP());
+            break;
+#endif
+
         default:
         {
 #ifdef DEBUG
@@ -8933,6 +8979,58 @@ void CodeGen::genEmitHelperCall(unsigned helper, int argSize, emitAttr retSize,
     regSet.verifyRegistersUsed(killMask);
 }
 
+insOpts CodeGen::OptsFromCFlags(insCflags flags)
+{
+    unsigned opts = 0x0;
+    if (flags & INS_FLAGS_CF)
+        opts |= INS_OPTS_EVEX_dfv_cf;
+    if (flags & INS_FLAGS_ZF)
+        opts |= INS_OPTS_EVEX_dfv_zf;
+    if (flags & INS_FLAGS_SF)
+        opts |= INS_OPTS_EVEX_dfv_sf;
+    if (flags & INS_FLAGS_OF)
+        opts |= INS_OPTS_EVEX_dfv_of;
+    return (insOpts)opts;
+}
+
+#ifdef TARGET_AMD64
+
+void CodeGen::genCodeForCCMP(GenTreeCCMP* ccmp)
+{
+    emitter* emit = GetEmitter();
+    assert(emit->UsePromotedEVEXEncoding());
+
+    genConsumeOperands(ccmp);
+    GenTree*  op1     = ccmp->gtGetOp1();
+    GenTree*  op2     = ccmp->gtGetOp2();
+    var_types op1Type = genActualType(op1->TypeGet());
+    var_types op2Type = genActualType(op2->TypeGet());
+    emitAttr  cmpSize = emitActualTypeSize(op1Type);
+    regNumber srcReg1 = op1->GetRegNum();
+
+    // No float support or swapping op1 and op2 to generate cmp reg, imm.
+    assert(!varTypeIsFloating(op2Type));
+    assert(!op1->isContainedIntOrIImmed());
+
+    // For the ccmp flags, invert the condition of the compare.
+    // For the condition, use the previous compare.
+    const GenConditionDesc& condDesc = GenConditionDesc::Get(ccmp->gtCondition);
+    instruction             ccmpIns  = JumpKindToCcmp(condDesc.jumpKind1);
+    insOpts                 opts     = OptsFromCFlags(ccmp->gtFlagsVal);
+
+    if (op2->isContainedIntOrIImmed())
+    {
+        GenTreeIntConCommon* intConst = op2->AsIntConCommon();
+        emit->emitIns_R_I(ccmpIns, cmpSize, srcReg1, (int)intConst->IconValue(), opts);
+    }
+    else
+    {
+        regNumber srcReg2 = op2->GetRegNum();
+        emit->emitIns_R_R(ccmpIns, cmpSize, srcReg1, srcReg2, opts);
+    }
+}
+#endif // TARGET_AMD64
+
 #if defined(DEBUG) && defined(TARGET_AMD64)
 
 /*****************************************************************************

src/coreclr/jit/compiler.h

@@ -7199,6 +7199,9 @@ class Compiler
     PhaseStatus optSwitchRecognition();
     bool optSwitchConvert(BasicBlock* firstBlock, int testsCount, ssize_t* testValues, weight_t falseLikelihood, GenTree* nodeToTest);
     bool optSwitchDetectAndConvert(BasicBlock* firstBlock);
+#if defined(TARGET_AMD64)
+    bool optSwitchDetectLikely(BasicBlock* firstBlock);
+#endif
 
     PhaseStatus optInvertLoops();    // Invert loops so they're entered at top and tested at bottom.
     PhaseStatus optOptimizeFlow();   // Simplify flow graph and do tail duplication

src/coreclr/jit/gentree.h

@@ -9562,7 +9562,7 @@ enum insCC : unsigned
 };
 #endif
 
-#if defined(TARGET_ARM64)
+#if defined(TARGET_ARM64) || defined(TARGET_AMD64)
 struct GenTreeCCMP final : public GenTreeOpCC
 {
     insCflags gtFlagsVal;

src/coreclr/jit/gtlist.h

@@ -244,11 +244,16 @@ GTNODE(JCC              , GenTreeCC          ,0,0,GTK_LEAF|GTK_NOVALUE|DBK_NOTHI
 GTNODE(SETCC            , GenTreeCC          ,0,0,GTK_LEAF|DBK_NOTHIR)
 // Variant of SELECT that reuses flags computed by a previous node with the specified condition.
 GTNODE(SELECTCC         , GenTreeOpCC        ,0,0,GTK_BINOP|DBK_NOTHIR)
-#ifdef TARGET_ARM64
-// The arm64 ccmp instruction. If the specified condition is true, compares two
+
+#if defined(TARGET_ARM64) || defined(TARGET_AMD64)
+// The arm64 and x86 ccmp instruction. If the specified condition is true, compares two
 // operands and sets the condition flags according to the result. Otherwise
 // sets the condition flags to the specified immediate value.
 GTNODE(CCMP             , GenTreeCCMP        ,0,0,GTK_BINOP|GTK_NOVALUE|DBK_NOTHIR)
+#endif
+
+
+#ifdef TARGET_ARM64
 // Maps to arm64 csinc/cinc instruction. Computes result = condition ? op1 : op2 + 1.
 // If op2 is null, computes result = condition ? op1 + 1 : op1.
 GTNODE(SELECT_INC       , GenTreeOp          ,0,0,GTK_BINOP|DBK_NOTHIR)

src/coreclr/jit/gtstructs.h

@@ -116,8 +116,10 @@ GTSTRUCT_1(AllocObj    , GT_ALLOCOBJ)
 GTSTRUCT_1(RuntimeLookup, GT_RUNTIMELOOKUP)
 GTSTRUCT_1(ArrAddr     , GT_ARR_ADDR)
 GTSTRUCT_2(CC          , GT_JCC, GT_SETCC)
-#ifdef TARGET_ARM64
+#if defined(TARGET_ARM64) || defined(TARGET_AMD64)
 GTSTRUCT_1(CCMP        , GT_CCMP)
+#endif
+#ifdef TARGET_ARM64
 GTSTRUCT_N(OpCC        , GT_SELECTCC, GT_SELECT_INCCC, GT_JCMP, GT_JTEST, GT_SELECT_INVCC, GT_SELECT_NEGCC)
 #else
 GTSTRUCT_3(OpCC        , GT_SELECTCC, GT_JCMP, GT_JTEST)

src/coreclr/jit/jitconfigvalues.h

@@ -443,6 +443,7 @@ RELEASE_CONFIG_INTEGER(EnableArm64Sve,              "EnableArm64Sve",
 RELEASE_CONFIG_INTEGER(EnableEmbeddedBroadcast,     "EnableEmbeddedBroadcast",   1) // Allows embedded broadcasts to be disabled
 RELEASE_CONFIG_INTEGER(EnableEmbeddedMasking,       "EnableEmbeddedMasking",     1) // Allows embedded masking to be disabled
 RELEASE_CONFIG_INTEGER(EnableApxNDD,                "EnableApxNDD",              0) // Allows APX NDD feature to be disabled
+RELEASE_CONFIG_INTEGER(EnableApxConditionalChaining, "EnableApxConditionalChaining",        0) // Allows APX conditional compare chaining
 
 // clang-format on
 

src/coreclr/jit/lower.cpp

@@ -4590,7 +4590,10 @@ GenTree* Lowering::LowerSelect(GenTreeConditional* select)
 // Return Value:
 //     True if relop was transformed and is now right before 'parent'; otherwise false.
 //
-bool Lowering::TryLowerConditionToFlagsNode(GenTree* parent, GenTree* condition, GenCondition* cond)
+bool Lowering::TryLowerConditionToFlagsNode(GenTree*      parent,
+                                            GenTree*      condition,
+                                            GenCondition* cond,
+                                            bool          allowMultipleFlagsChecks)
 {
     JITDUMP("Lowering condition:\n");
     DISPTREERANGE(BlockRange(), condition);
@@ -4612,6 +4615,11 @@ bool Lowering::TryLowerConditionToFlagsNode(GenTree* parent, GenTree* condition,
         GenTree* relopOp2 = relop->gtGetOp2();
 
 #ifdef TARGET_XARCH
+        if (!allowMultipleFlagsChecks && cond->IsFloat())
+        {
+            return false;
+        }
+
         // Optimize FP x != x to only check parity flag. This is a common way of
         // checking NaN and avoids two branches that we would otherwise emit.
         if (optimizing && (cond->GetCode() == GenCondition::FNEU) && relopOp1->OperIsLocal() &&

src/coreclr/jit/lower.h

@@ -89,7 +89,7 @@ class Lowering final : public Phase
     void ContainCheckReturnTrap(GenTreeOp* node);
     void ContainCheckLclHeap(GenTreeOp* node);
     void ContainCheckRet(GenTreeUnOp* ret);
-#ifdef TARGET_ARM64
+#if defined(TARGET_ARM64) || defined(TARGET_AMD64)
     bool      TryLowerAndOrToCCMP(GenTreeOp* tree, GenTree** next);
     insCflags TruthifyingFlags(GenCondition cond);
     void      ContainCheckConditionalCompare(GenTreeCCMP* ccmp);
@@ -161,7 +161,10 @@ class Lowering final : public Phase
     GenTree*   LowerCompare(GenTree* cmp);
     GenTree*   LowerJTrue(GenTreeOp* jtrue);
     GenTree*   LowerSelect(GenTreeConditional* cond);
-    bool       TryLowerConditionToFlagsNode(GenTree* parent, GenTree* condition, GenCondition* code);
+    bool       TryLowerConditionToFlagsNode(GenTree*      parent,
+                                            GenTree*      condition,
+                                            GenCondition* code,
+                                            bool          allowMultipleFlagChecks = true);
     GenTreeCC* LowerNodeCC(GenTree* node, GenCondition condition);
     void       LowerJmpMethod(GenTree* jmp);
     void       LowerRet(GenTreeOp* ret);