Support MO_{Add,Sub}IntC and MO_Add2 in the LLVM backend

This includes:

- Adding new LlvmType called LMStructP that represents an unpacked
  struct (this is necessary since LLVM's instructions the
  llvm.sadd.with.overflow.* return an unpacked struct).

- Modifications to LlvmCodeGen.CodeGen to generate the LLVM
  instructions for the primops.

- Modifications to StgCmmPrim to actually use those three instructions
  if we use the LLVM backend (so far they were only used for NCG).

Test Plan: validate

Reviewers: austin, rwbarton, bgamari

Reviewed By: bgamari

Subscribers: thomie, bgamari

Differential Revision: https://phabricator.haskell.org/D991

GHC Trac Issues: #9430

3 files changed, 28 insertions, 1 deletions

diff --git a/compiler/llvmGen/Llvm/AbsSyn.hs b/compiler/llvmGen/Llvm/AbsSyn.hs
index b0eae2cbfe..8a53df00fe 100644
--- a/compiler/llvmGen/Llvm/AbsSyn.hs
+++ b/compiler/llvmGen/Llvm/AbsSyn.hs
@@ -209,6 +209,14 @@ data LlvmExpression
   | Extract LlvmVar LlvmVar
 
   {- |
+    Extract a scalar element from a structure
+      * val: The structure
+      * idx: The index of the scalar within the structure
+    Corresponds to "extractvalue" instruction.
+  -}
+  | ExtractV LlvmVar Int
+
+  {- |
     Insert a scalar element into a vector
       * val:   The source vector
       * elt:   The scalar to insert
diff --git a/compiler/llvmGen/Llvm/PpLlvm.hs b/compiler/llvmGen/Llvm/PpLlvm.hs
index 0b3deac764..db9ef1fccf 100644
--- a/compiler/llvmGen/Llvm/PpLlvm.hs
+++ b/compiler/llvmGen/Llvm/PpLlvm.hs
@@ -239,6 +239,7 @@ ppLlvmExpression expr
         Cast       op from to       -> ppCast op from to
         Compare    op left right    -> ppCmpOp op left right
         Extract    vec idx          -> ppExtract vec idx
+        ExtractV   struct idx       -> ppExtractV struct idx
         Insert     vec elt idx      -> ppInsert vec elt idx
         GetElemPtr inb ptr indexes  -> ppGetElementPtr inb ptr indexes
         Load       ptr              -> ppLoad ptr
@@ -430,6 +431,12 @@ ppExtract vec idx =
     <+> ppr (getVarType vec) <+> ppName vec <> comma
     <+> ppr idx
 
+ppExtractV :: LlvmVar -> Int -> SDoc
+ppExtractV struct idx =
+    text "extractvalue"
+    <+> ppr (getVarType struct) <+> ppName struct <> comma
+    <+> ppr idx
+
 ppInsert :: LlvmVar -> LlvmVar -> LlvmVar -> SDoc
 ppInsert vec elt idx =
     text "insertelement"
diff --git a/compiler/llvmGen/Llvm/Types.hs b/compiler/llvmGen/Llvm/Types.hs
index a9d81a1828..b3b173096b 100644
--- a/compiler/llvmGen/Llvm/Types.hs
+++ b/compiler/llvmGen/Llvm/Types.hs
@@ -50,7 +50,8 @@ data LlvmType
   | LMVector Int LlvmType -- ^ A vector of 'LlvmType'
   | LMLabel               -- ^ A 'LlvmVar' can represent a label (address)
   | LMVoid                -- ^ Void type
-  | LMStruct [LlvmType]   -- ^ Structure type
+  | LMStruct [LlvmType]   -- ^ Packed structure type
+  | LMStructU [LlvmType]  -- ^ Unpacked structure type
   | LMAlias LlvmAlias     -- ^ A type alias
   | LMMetadata            -- ^ LLVM Metadata
 
@@ -70,6 +71,7 @@ instance Outputable LlvmType where
   ppr (LMLabel        ) = text "label"
   ppr (LMVoid         ) = text "void"
   ppr (LMStruct tys   ) = text "<{" <> ppCommaJoin tys <> text "}>"
+  ppr (LMStructU tys  ) = text "{" <> ppCommaJoin tys <> text "}"
   ppr (LMMetadata     ) = text "metadata"
 
   ppr (LMFunction (LlvmFunctionDecl _ _ _ r varg p _))
@@ -326,6 +328,16 @@ llvmWidthInBits dflags (LMVector n ty) = n * llvmWidthInBits dflags ty
 llvmWidthInBits _      LMLabel         = 0
 llvmWidthInBits _      LMVoid          = 0
 llvmWidthInBits dflags (LMStruct tys)  = sum $ map (llvmWidthInBits dflags) tys
+llvmWidthInBits _      (LMStructU _)   =
+    -- It's not trivial to calculate the bit width of the unpacked structs,
+    -- since they will be aligned depending on the specified datalayout (
+    -- http://llvm.org/docs/LangRef.html#data-layout ). One way we could support
+    -- this could be to make the LlvmCodeGen.Ppr.moduleLayout be a data type
+    -- that exposes the alignment information. However, currently the only place
+    -- we use unpacked structs is LLVM intrinsics that return them (e.g.,
+    -- llvm.sadd.with.overflow.*), so we don't actually need to compute their
+    -- bit width.
+    panic "llvmWidthInBits: not implemented for LMStructU"
 llvmWidthInBits _      (LMFunction  _) = 0
 llvmWidthInBits dflags (LMAlias (_,t)) = llvmWidthInBits dflags t
 llvmWidthInBits _      LMMetadata      = panic "llvmWidthInBits: Meta-data has no runtime representation!"