GEP Loop Strength Reduction pass - add optional IGC flags to

enable mul expressions and non-constant int steps

Adds new flags:
 1. EnableGEPLSRUnknownConstantStep - If enabled, allows expressions
    with steps unknown at compilation time. Disabled by default.
 2. EnableGEPLSRMulExpr - If enabled, allows expressions with mul.
    Disabled by default. If enabled, also enables
    EnableGEPLSRUnknownConstantStep.

Author: pkwasnie-intel

IGC/Compiler/Optimizer/OpenCLPasses/GEPLoopStrengthReduction/GEPLoopStrengthReduction.cpp

@@ -937,6 +937,9 @@ void Analyzer::analyzeGEP(GetElementPtrInst *GEP)
     if (!deconstructSCEV(S, Start, Step))
         return;
 
+    if (Step->getSCEVType() != scConstant && IGC_IS_FLAG_DISABLED(EnableGEPLSRUnknownConstantStep) && IGC_IS_FLAG_DISABLED(EnableGEPLSRMulExpr))
+        return;
+
     if (S->getType() != Start->getType())
         Start = isa<SCEVSignExtendExpr>(S) ? SE.getSignExtendExpr(Start, S->getType()) : SE.getZeroExtendExpr(Start, S->getType());
 
@@ -1115,6 +1118,9 @@ bool Analyzer::deconstructSCEV(const SCEV *S, const SCEV *&Start, const SCEV *&S
     // Warning: GEP's new index will not be a constant integer, but a new SCEV expression.
     if (auto *Mul = dyn_cast<SCEVMulExpr>(S))
     {
+        if (IGC_IS_FLAG_DISABLED(EnableGEPLSRMulExpr))
+            return false;
+
         // SCEVAddRecExpr will be SCEV with step != 0. Any other SCEV is a multiplier.
         bool FoundAddRec = false;
         SCEVHelper::SCEVMulBuilder StartBuilder(SE), StepBuilder(SE);

IGC/Compiler/tests/GEPLoopStrengthReduction/illegal_types.ll

@@ -7,8 +7,8 @@
 ;============================ end_copyright_notice =============================
 
 ; REQUIRES: regkeys
-; RUN: igc_opt --regkey=EnableGEPLSRAnyIntBitWidth=0 -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s --check-prefix=CHECK-BLOCK-ILLEGAL
-; RUN: igc_opt --regkey=EnableGEPLSRAnyIntBitWidth=1 -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s --check-prefix=CHECK-ALLOW-ILLEGAL
+; RUN: igc_opt --regkey=EnableGEPLSRMulExpr=1 --regkey=EnableGEPLSRAnyIntBitWidth=0 -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s --check-prefix=CHECK-BLOCK-ILLEGAL
+; RUN: igc_opt --regkey=EnableGEPLSRMulExpr=1 --regkey=EnableGEPLSRAnyIntBitWidth=1 -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s --check-prefix=CHECK-ALLOW-ILLEGAL
 ;
 ; Test for illegal types in SCEV expressions.
 

IGC/Compiler/tests/GEPLoopStrengthReduction/one_access_mulexpr_decrement.ll

@@ -6,7 +6,8 @@
 ;
 ;============================ end_copyright_notice =============================
 
-; RUN: igc_opt -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s
+; REQUIRES: regkeys
+; RUN: igc_opt --regkey=EnableGEPLSRMulExpr=1 -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s
 
 ; Reduced index is expressed with SCEVMulExpr.
 

IGC/Compiler/tests/GEPLoopStrengthReduction/one_access_mulexpr_increment.ll

@@ -6,7 +6,8 @@
 ;
 ;============================ end_copyright_notice =============================
 
-; RUN: igc_opt -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s
+; REQUIRES: regkeys
+; RUN: igc_opt --regkey=EnableGEPLSRMulExpr=1 -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s
 
 ; Reduced index is expressed with SCEVMulExpr.
 

IGC/Compiler/tests/GEPLoopStrengthReduction/one_access_unknown_constant_step.ll

@@ -6,7 +6,8 @@
 ;
 ;============================ end_copyright_notice =============================
 
-; RUN: igc_opt -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s
+; REQUIRES: regkeys
+; RUN: igc_opt --regkey=EnableGEPLSRUnknownConstantStep=1 -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s
 
 ; Pointer is indexed with an uknown value. As long as the step is constant, we can optimize GEP.
 

IGC/Compiler/tests/GEPLoopStrengthReduction/two_accesses_unknown_constant_step.ll

@@ -6,7 +6,8 @@
 ;
 ;============================ end_copyright_notice =============================
 
-; RUN: igc_opt -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s
+; REQUIRES: regkeys
+; RUN: igc_opt --regkey=EnableGEPLSRUnknownConstantStep=1 -debugify --igc-gep-loop-strength-reduction -check-debugify -S < %s 2>&1 | FileCheck %s
 
 ; Pointer is indexed with an uknown value. As long as the step is constant, we can optimize GEP.
 

IGC/common/igc_flags.h

@@ -293,6 +293,8 @@ DECLARE_IGC_REGKEY(bool, RunGEPLSRAfterLICM, false, "Runs GEP Loop Strength Redu
 DECLARE_IGC_REGKEY(DWORD, GEPLSRThresholdRatio, 100, "Ratio for register pressure threshold in GEP Loop Strength Reduction pass", true)
 DECLARE_IGC_REGKEY(bool, EnableGEPLSRToPreheader, true, "Enables reduction to loop's preheader in GEP Loop Strength Reduction pass", true)
 DECLARE_IGC_REGKEY(bool, EnableGEPLSRAnyIntBitWidth, false, "Experimental: Enables reduction of SCEV with illegal integers. Requires legalization pass to clear up expanded code.", true)
+DECLARE_IGC_REGKEY(bool, EnableGEPLSRMulExpr, false, "Experimental: Enables reduction of SCEV with mul expression.", true)
+DECLARE_IGC_REGKEY(bool, EnableGEPLSRUnknownConstantStep, false, "Experimental: Enables reduction of SCEV with step expressed with constant value unknown at compilation time.", true)
 DECLARE_IGC_REGKEY(DWORD, FPRoundingModeCoalescingMaxDistance, 20, "Max distance in instructions for reordering FP instructions with common rounding mode", false)
 DECLARE_IGC_REGKEY(bool, DisableDotAddToDp4aMerge, false, "Disable Dot and Add ops to Dp4a merge optimization.", false)
 DECLARE_IGC_REGKEY(bool, DisableLoopSplitWidePHIs, false, "Disable splitting of loop PHI values to eliminate subvector extract operations", false)