Understanding the hardware and using it efficiently – Computing resources of a CPU – Pipelining – Branch prediction and hardware loop unrolling ● Conditional code vs efficiency ● Optimizing conditional v2[i+2]: v1[i+2]: a[i+2]:Branchless Computing 24 BRANCH PREDICTION: ANTIDOTE TO BRANCHES ● Well-pipelined code: a += v1[i] + v2[i] ● CPUs have branch predi ctorsBranchless Computing 25 LOOP UNROLLING cmp[i]:v3[i]==0 jump if true a[i]:a+=v1[i]+v2[i] jump a[i]:a+=v1[i]*v2[i] ...Branchless Computing 28 BRANCH PREDICTION: ANTIDOTE TO BRANCHES ● Speculatively pipelined code: a += (v3[i]) ? (v1[i]+v2[i]) :

serving a specific purpose:  master - This is the Laravel release branch. Active development does not happen on this branch. This branch is only for the most recent, stable Laravel core code. When you are downloading directly from this master branch. Do not make pull requests to this branch. 122  develop - This is the working development branch. All proposed code changes and contributions contributions by the community are pulled into this branch. When you make a pull request to the Laravel project, this is the branch you want to pull-request into. Once certain milestones have been reached and/or

rs1,rs2 Shift Right Arithmetic R SRA rd,rs1,rs2 Shift Right Arith. Imm. I SRAI rd,rs1,shamt Branch = 0 (BEQ rs,x0,imm) J BEQZ rs,imm Aritmética ADD R ADD rd,rs1,rs2 Jump (uses JAL x0,imm) rs2,imm Branches Branch = B BEQ rs1,rs2,imm Float Store Double CS C.FSD rs1′,rs2′,imm Branch ≠ B BNE rs1,rs2,imm Float Store Double SP CSS C.FSDSP rs2,imm Branch < B BLT rs1,rs2,imm ADD CR C.ADD rd,rs1 Branch ≥ B BGE rs1,rs2,imm ADD Immediate CI C.ADDI rd,imm Branch < Unsigned B BLTU rs1,rs2,imm ADD SP Imm * 16 CI C.ADDI16SP x0,imm Branch ≥ Unsigned B BGEU rs1,rs2

{ // do something } if and else are keywords. Like many other programming languages, the else branch is optional. The InitSimpleStatement portion is also optional. It must be a simple statement (§11) if-else control flow forms one implicit code block, one if branch explicit code block and one optional else branch code block. The two branch code blocks are both nested in the implicit code block. Upon Upon execution, if Condition expression results in true, then the if branch block will get executed, otherwise, the else branch block will get executed. Example: package main import ( "fmt" "math/rand"

// do something 5| } if and else are keywords. Like many other programming languages, the else branch is optional. The InitSimpleStatement portion is also optional. It must be a simple statement (§11) if-else control flow forms one implicit code block, one if branch explicit code block and one optional else branch code block. The two branch code blocks are both nested in the implicit code block. Upon Upon execution, if Condition expression results in true, then the if branch block will get executed, otherwise, the else branch block will get executed. Example: 1| package main 2| 3| import ( 4|

restricted: The new value must not lead to a change of the active object branch. Also, when the �elds of a particular branch are speci�ed during object construction, the corresponding discriminator value changing the active object branch, replace the old object in memory with a new one completely: Starting with version 0.20 system.reset cannot be used anymore to support object branch changes as this never possible values of the discriminator variable in a case statement branch are a subset of discriminator values for the selected object branch, the initialization is considered valid. This analysis only works

// do something 5| } if and else are keywords. Like many other programming languages, the else branch is optional. The InitSimpleStatement portion is also optional. It must be a simple statement (§11) if-else control flow forms one implicit code block, one if branch explicit code block and one optional else branch code block. The two branch code blocks are both nested in the implicit code block. Upon Upon execution, if Condition expression results in true, then the if branch block will get executed, otherwise, the else branch block will get executed. Example: 1| package main 2| 3| import ( 4|

rs1,rs2 Shift Right Arithmetic R SRA rd,rs1,rs2 Shift Right Arith. Imm. I SRAI rd,rs1,shamt Branch = 0 (BEQ rs,x0,imm) J BEQZ rs,imm Arithmetic ADD R ADD rd,rs1,rs2 Jump (uses JAL x0,imm) rs2,imm Branches Branch = B BEQ rs1,rs2,imm Float Store Double CS C.FSD rs1′,rs2′,imm Branch ≠ B BNE rs1,rs2,imm Float Store Double SP CSS C.FSDSP rs2,imm Branch < B BLT rs1,rs2,imm Arithmetic ADD CR C.ADD rd,rs1 Branch ≥ B BGE rs1,rs2,imm ADD Immediate CI C.ADDI rd,imm Branch < Unsigned B BLTU rs1,rs2,imm ADD SP Imm * 16 CI C.ADDI16SP x0,imm Branch ≥ Unsigned B BGEU rs1,rs2

bool cond) { int var = 0; // branch 1 if (p != nullptr) { var = 1; } // branch 2 if (cond) { var = 2; p = nullptr; } // branch 3 if (var == 1) { *p = 42; Not taking branch 1, but taking branch 3 • All warnings on infeasible paths are noise • Need info on the whole state! void path_sensitive(int *p, bool cond) { int var = 0; // branch 1 if (p (p != nullptr) { var = 1; } // branch 2 if (cond) { var = 2; p = nullptr; } // branch 3 if (var == 1) { *p = 42; // Null dereference? } }Flow-sensitive analysis

many other languages. This value is simply the return value of the last executed statement in the branch that was chosen, so julia> x = 3 3CHAPTER 9. CONTROL FLOW 92 julia> if x > 0 "positive!" else LTS version of Julia is versioned according to SemVer as v1.6.x; this branch will continue to receive bugfixes until a new LTS branch is chosen, at which point the v1.6.x series will no longer received arguments are evaluated first. In some cases, using ifelse instead of an if statement can eliminate the branch in generated code and provide higher performance in tight loops. Examples julia> ifelse(1 > 2,